Adventist.org says people point out faults with Ellen White with great satisfaction. Perhaps some do.
However, every branch of the church has been deceived into believing innumerable false doctrines and hoodwinked into following countless numbers of false teachers and prophets. Sadly, some of these pied pipers are even very popular among evangelicals.
While they do not claim to be prophets, leaders like Rick Warren have considerable influence and very subtly lead people horribly astray. Brian McLaren, a former pastor and a very well known author and speaker, claims to be a theologian but, in reality, is one of the very dangerous wolves that Paul warned the church about. You can add to the list of false and dangerous teachers the entire stable of Word-Faith/Positive Confession teachers, the innumerable 'Christian' leaders who encourage people to walk labyrinths, speak in tongues, get 'slain in the spirit' and indulge in contemplative prayer - all doctrines that directly derive from the occult and have nothing to do with the SDA church.
See The Occult Take Over of The Once Christian Church
There is absolutely no "satisfaction" in bringing any false teachings to the attention of believers. It is done in the hope that someone out there will see the truth and not only shun those who teach wrong doctrine, but speak out against them. Some of the very important details that Ellen White got wrong are shared by much of the modern church, or they have their own equally inaccurate and unbiblical versions.
Ellen White's Life and Career in a Nutshell
Ellen Gould Harmon was born to Robert and Eunice Harmon on November 26, 1827, in Maine. When she was nine or ten, she was permanently disfigured when a fellow student hit her in the head with a rock. This incident put her in a coma for several weeks and forced her to miss much schooling. She eventually had to give up on the idea of gaining a formal education.
In 1840, when she was about 13, Ellen White and her family began attending William Miller's meetings and embraced the Adventist faith including the belief that Christ would return in 1844. When this proved to be a non-event, Ellen claimed to have received a vision of being transported to heaven. This and her many subsequent visions and dreams were accepted as God given revelations, and she soon became a spiritual leader, guiding the Adventist church in all doctrine.
On August 30, 1846, Ellen Harmon married James White - a young Adventist preacher. The couple had four children and traveled extensively spreading the Adventist faith. When they moved to Battle Creek, Michigan in 1855, that small town became the hub of Adventism. In 1863 Ellen White claimed to have been given a vision about health reform, which led to her followers adopting a vegetarian diet and avoiding tea and coffee along with other "unhealthy" substances.
She and her husband also traveled extensively across America addressing large audiences. As the Adventist movement continued to spread, Ellen White wrote almost continuously - 40 books, close to 5,000 periodical articles and numerous letters - considered to be an authoritative source of truth. It is said that, during the course of her life, her Testimonies for the Church grew from sixteen pages to nine volumes.
James White died in 1881, after which Ellen preached in various Adventist church, and attended conferences and camp meetings. She also traveled further afield spending a couple of years in England, a few in Europe and nine in Australia. The final fifteen years of her life were spent in Elmshaven, California, a time that was devoted to the organization of the denomination as well as more writing. In 1901 she founded the Southern Publishing Association in Nashville, Tennessee, and in 1903 she played a part in moving the national denominational headquarters to Washington, D.C.
When Ellen White died at the age of 87 in 1915, there were about 140,000 Adventists on the face of the planet. They now number approximately 18.5 million with members spread around the world.
Ellen White... Spiritual Leader and 'Prophet'
Ellen White is an acknowledged spiritual leader of the Seventh Day Adventist church. Although she called herself a messenger of the Lord, rather than a "prophet", she knew and accepted that others believed her to be one.
I have had no claims to make, only that I am instructed that I am the Lord's messenger; that He called me in my youth to be His messenger, to receive His word, and to give a clear and decided message in the name of the Lord Jesus.... Why have I not claimed to be a prophet? Because in these days many who boldly claim that they are prophets are a reproach to the cause of Christ; and because my work includes much more than the word "prophet" signifies. 
She wrote that she never claimed to be a prophet but if others called her one, she had "no controversy with them" . Her "commission" embraced the work of a prophet, but did not end there"  and that she never expressed her own ideas but only what the Lord had showed her...
In ancient times God spoke to men by the mouth of prophets and apostles. In these days he speaks to them by the testimonies of his Spirit. 
As the Spirit of God has opened to my mind the great truths of his Word, and the scenes of the past and the future, I have been bidden to make known to others what has thus been revealed" 
Thus ignoring her warnings and reproofs was tantamount to 'insulting the Spirit of God'
Yet now when I send you a testimony of warning and reproof, many of you declare it to be merely the opinion of Sister White. You have thereby insulted the Spirit of God. 
On December 26, 1904, towards the end of her life, Ellen White wrote to a 'Brother Harper'. While I do not know how many books had been published by the time the letter was written, I presume a good many of them were. What is made very clear is that she believed their content was God given. The letter began with the words.
Sister Hall has just read me your letter to her. I am glad that you are having success in selling my books; for thus you are giving to the world the light that God has given me. These books contain clear, straight, unalterable truth and they should certainly be appreciated. The instruction they contain is not of human production. 
A letter addressed to "Brethren and Sisters in Battle Creek" and dated June 20, 1882, was apparently written because she had sent a testimony to Uriah Smith with the request that it be read to the church. He had however, withheld it for several weeks. In it Ellen White said that the apostle Paul was "set for the defense of the church" and when reports of "anarchy and division" came to his notice, his reproofs were "written just as much under the inspiration of the Spirit of God as were any of his epistles". However, some believed that Paul's reproofs were only "his opinion" and "God had not spoken to them through Paul" , thus their own judgments were as good as the apostles. She went on to say...
So it is with many among our people who have drifted away from the old landmarks, and who have followed their own understanding. What a great relief it would be to such could they quiet their conscience with the belief that my work is not of God. But your unbelief will not change the facts in the case. You are defective in character, in moral and religious experience. Close your eyes to the fact if you will; but this does not make you one particle more perfect. [Pg 46]
Eld. Smith, I was more grieved than I can express to find you again working on the side of the enemy. You will find quite a number who will strengthen you in your position; the leaven is working. You pronounce my work human, not actuated by the Spirit of God... If you seek to turn aside the counsel of God to suit yourselves, if you lessen the confidence of God's people in the testimonies He has sent them, you are rebelling against God as certainly as were Korah, Dathan, and Abiram... As Christ's ambassador, I would say to you: Be careful what positions you take. This is God's work, and you must render to Him an account for the manner in which you treat His message... [Pg 48]
In these letters which I write, in the testimonies I bear, I am presenting to you that which the Lord has presented to me. I do not write one article in the paper expressing merely my own ideas. They are what God has opened before me in vision - the precious rays of light shining from the throne. [Pg.49] 
Ellen White's Position in The SDA Church
That the Seventh Day Adventists hold Ellen White in high esteem (to put it mildly) is of no doubt. In answer to the question "Do you still believe that Ellen White was a prophetess?" The British Union Conference of Seventh-day Adventists says (All Emphasis Added)
"Yes, though she never claimed that title. She preferred to describe herself as God's messenger, or servant, but in today's language we would say that she had the spiritual gift of prophecy. Ellen White used this gift from 1844, when she was just 17, to 1915, the year of her death. We believe that the main purpose of her spiritual gift was to build up the Seventh-day Adventist Church in its early stages.... Her writings are not in any way a substitute for scripture but many Seventh-day Adventists have come to appreciate the Bible better after reading her writings". 
In fact, number 18 of the 28 fundamental beliefs of the church is entitled The Gift of Prophecy. It reads (Emphasis Added)
The Scriptures testify that one of the gifts of the Holy Spirit is prophecy. This gift is an identifying mark of the remnant church and we believe it was manifested in the ministry of Ellen G. White. Her writings speak with prophetic authority and provide comfort, guidance, instruction, and correction to the church. They also make clear that the Bible is the standard by which all teaching and experience must be tested. 
According to the quote above, Ellen White's writings make clear that all teaching and experience are to be tested by the Bible. She might have said that but, in reality, she firmly held to the premise that any interpretation of the Bible that contradicted her visions was faulty.
Arguments from the Bible That Contradict SDA beliefs Are a "Mistake"
The "light" received by the early Adventists was so implicitly believed to be given by God Himself that, according to Ellen White, no contrary "after-suppositions" were to be entertained. And any application of the Scriptures that contradicted "one pillar of the foundation" that God had supposedly sustained for half a century, was a "mistake". Additionally, any one who brought up these supposedly wrong interpretations of God's word, did not know how wonderfully the Holy Spirit had given power to the past Adventist messages.
In a letter written to a J. A. Burden in 1905, Ellen White wrote
I have been pleading with the Lord for strength and wisdom to reproduce the writings of the witnesses who were confirmed in the faith in the early history of the message. After the passing of the time in 1844, they received the light and walked in the light.... No after-suppositions contrary to the light God has given are to be entertained...
We are not to receive the words of those who come with a message that contradicts the special points of our faith. They gather together a mass of Scripture and pile it as proof around their asserted theories. This has been done over and over again during the past fifty years. And while the Scriptures are God's Word, and are to be respected, the application of them, if such application moves one pillar of the foundation that God has sustained these fifty years, is a great mistake. He who makes such an application knows not the wonderful demonstration of the Holy Spirit that gave power and force to the past messages that have come to the people of God. 
In other words, Ellen White's visions and dreams were the truth, and any opposing arguments - even from the Bible - were not to be heeded. The "mass of Scripture" others gathered to make their point were wrong if they contradicted her visions. Yet, by her own admission, she was unable to comprehend the meaning of Scripture without the visions. In other words, she did not have the ability to discern whether or not the visions were in harmony with the word of God.
When they came to the point in their study where they said, "We can do nothing more,” the Spirit of the Lord would come upon me. I would be taken off in vision, and a clear explanation of the passages we had been studying would be given me...
During this whole time I could not understand the reasoning of the brethren. My mind was locked, as it were, and I could not comprehend the meaning of the scriptures we were studying. This was one of the greatest sorrows of my life. I was in this condition of mind until all the principal points of our faith were made clear to our minds, in harmony with the Word of God. The brethren knew that, when not in vision, I could not understand these matters, and they accepted, as light directly from heaven, the revelations given. 
Part I. The Biblical Tests For a Genuine Prophet of God
The 'Orchard' Test
Adventist.org says we can know Ellen White's prophetic gift was genuine because she passes all the Biblical tests for a true prophet. One of their tests of a 'true prophet' is ...
The Orchard Test - Matthew 7:20. The orchard test takes time. Ellen White lived and worked for 70 years under the critical eyes of millions of people, largely skeptical, doubtful, suspicious, and in some cases openly hostile. Any fault or inconsistency was and still is exposed with great satisfaction by her opponents. Nevertheless, the fruit of her life and labor attests to her sincerity, zeal, and Christian piety. 
Matthew 7:20 says "So then, you will know them by their fruits". However, if you read the verse in context, Jesus is speaking of false prophets who come disguised in sheep's clothing but are, in reality, ravening wolves.
Beware of the false prophets, who come to you in sheep's clothing, but inwardly are ravenous (Gk. harpax) wolves. "You will know them by their fruits. Grapes are not gathered from thorn bushes nor figs from thistles, are they? "So every good tree bears good fruit, but the bad tree bears bad fruit. "A good tree cannot produce bad fruit, nor can a bad tree produce good fruit. "Every tree that does not bear good fruit is cut down and thrown into the fire. "So then, you will know them by their fruits. (NASB)
The Wolves/False Prophets Have a Purpose
Although the Greek word harpax has been translated 'ravenous', the word comes from harpazo which means to seize or carry off by force - to snatch away. In other words, the wolves snatch away sheep.
Other New Testament verses give us a little more insight. When he warned about savage wolves who would infiltrate the flock after his departure, Paul said they would endeavor to draw believers away from the truth by speaking "perverse things".
"I know that after my departure savage wolves will come in among you, not sparing the flock; and from among your own selves men will arise, speaking perverse (Gk. diastrepho) things, to draw away the disciples after them. (Acts 20:29-30 NASB)
The Greek word diastrepho means to distort, misinterpret, twist, corrupt, or turn away. Acts 13 provides more than one good example of how the word is used..
But Elymas the magician (for so his name is translated) was opposing them, seeking to turn (Gk. diastrepho) the proconsul away from the faith. But Saul, who was also known as Paul, filled with the Holy Spirit, fixed his gaze on him, and said, "You who are full of all deceit and fraud, you son of the devil, you enemy of all righteousness, will you not cease to make crooked (Gk. diastrepho) the straight ways of the Lord? (Acts 13:8-10 NASB)
In summary, voracious wolves distort, misinterpret, and twist the word and ways of God in order to draw (snatch) believers away.
What "Fruits" Can We Can Judge Them By?
While there is no question that we should pay attention to any church leader's behavior, lifestyle, etc. However since Jesus was speaking very specifically about false prophets, there is only one criteria or "fruit" that we can judge any prophet by.
Because all prophets primarily stand or fall on what they say, their words have to line up with the word of God, and any prophecies they make have to come unerringly true. In other words, the fruit of a prophet are the words that he speaks.
The numerous Biblical warnings about false teachers and prophets were not a matter of someone in the ancient past having nothing better to do that day. It was, and is, an extremely important issue because believing 'prophecies' that didn't originate with the Father is very likely to lead you off His path. Which is why it is imperative to follow the Biblical guidelines for determining who is and who isn't a true prophet. We can be grateful that the Lord has given us very objective criteria to guard against blindly believing everyone who claims to have had a dream or a vision. In other words we can, without the shadow of a doubt, know whether or not Ellen White's "spirit of prophecy" was of divine origin.
Adventist.org says the fruit of Ellen White's life and labor "attests to her sincerity, zeal, and Christian piety". While there is little question that she exhibited these traits, there is such a thing as mis-directed zeal, misguided sincerity and false piety. Good traits do not amount to a brass farthing if what the person said/wrote, or claimed to have seen in a vision contradicted the word of God, or if any of their prophecies failed to come to pass. Unfortunately, the only fruit of Ellen White's life and labor seems to be that hundred of thousands of people have been led into false beliefs.
Please remember that if her gifts were of Divine origin, it would have been impossible for her to be wrong on any doctrinal matter - or even other issues that she claimed she was "shown".
And, as a by the way, one cannot compare her inaccuracies with Nathan who prematurely told king David to go ahead with his plans for building the temple because, as he said the Lord was with David. (2 Samuel 7:3). David had a commendable idea which Nathan, as a pious man, not as a prophet, whole-heartedly endorsed. His statement "the Lord is with you" did not necessarily mean the Lord approved of David's plan to build a temple. The phrase is used a few times in the Old Testament to simply state that the Lord was on the side of the individual concerned. And, as we know, the Lord was certainly on David's side for a variety of reasons.
The next five pages cover Ellen White's failed prophecies, the many times her statements contradicted the word of God, examples of her quoting only one part of a Bible verse in order to prove a point (the other part contradicted what she said), the doctrines that she got wrong (some of them shared by the mainstream church), and that her health reform she claimed was given by God, included some very erroneous beliefs. They also cover that fact that she so often contradicted herself and, equally often, displayed rank hypocrisy not following her own teachings on food, photography etc.
Finally, one has to compare Ellen White's visions with those of the Bible.
Dreams and Visions ... Mark of a True Prophet of God?
Adventist.org outlines five tests of a true prophet, the first of which is that all genuine prophets have dreams and visions. Based on an estimate made by Ellen White's grandson Arthur White, she is said to have had roughly 2,000 of these during her ministry.  See Footnote I. On the other hand, in 1868, her husband James White estimated far fewer visions, saying that EW "probably had, during the past twenty-three years, between one and two hundred visions. 
There is no question that God frequently used visions to reveal or further His plans. In the Old Testament, Abraham, Jacob, Joseph, Isaiah, Samuel and, most notably, Daniel were all given them, as were Zacharias, Joseph, Peter and again, very notably, the apostle John in the New Testament.
However, dreams and visions were never limited to the people of God. In the Old Testament Pharaoh's cupbearer and baker, who were both imprisoned with Joseph, were given dreams (Genesis 40), as was the Pharaoh himself (Genesis 41). Nebuchadnezzar, king of Babylon's famous dream (See interpretation HERE) is well known to most Christians.
Besides which, numerous passages in the Bible warn about prophets who saw false and foolish visions that came not from the Lord, but from their own minds and imaginations.
Your prophets have seen for you false and foolish visions; and they have not exposed your iniquity so as to restore you from captivity, But they have seen for you false and misleading oracles. (Lamentations 2:14 NASB)
Then the Lord said to me, "The prophets are prophesying falsehood in My name. I have neither sent them nor commanded them nor spoken to them; they are prophesying to you a false vision, divination, futility and the deception of their own minds. (Jeremiah 14:14 NASB)
Thus says the Lord of hosts, "Do not listen to the words of the prophets who are prophesying to you. They are leading you into futility; They speak a vision of their own imagination, Not from the mouth of the Lord. (Jeremiah 23:16 NASB)
It is also stressed that these prophets will not get off scot-free. The Lord specifically says they have led His people astray and His hand will be against them
Behold, I am against the prophets," declares the Lord, "who use their tongues and declare, 'The Lord declares.' "Behold, I am against those who have prophesied false dreams," declares the Lord, "and related them and led My people astray by their falsehoods and reckless boasting; yet I did not send them or command them, nor do they furnish this people the slightest benefit," declares the Lord. (Jeremiah 23:31-32 NASB)
Thus says the Lord God, "Woe to the foolish prophets who are following their own spirit and have seen nothing. "O Israel, your prophets have been like foxes among ruins. "You have not gone up into the breaches, nor did you build the wall around the house of Israel to stand in the battle on the day of the Lord. "They see falsehood and lying divination who are saying, 'The Lord declares,' when the Lord has not sent them; yet they hope for the fulfillment of their word. "Did you not see a false vision and speak a lying divination when you said, 'The Lord declares, God, "Because you have spoken falsehood and seen a lie, therefore behold, I am against you," declares the Lord God. "So My hand will be against the prophets who see false visions and utter lying divinations. They will have no place in the council of My people, nor will they be written down in the register of the house of Israel, nor will they enter the land of Israel, that you may know that I am the Lord God. (Ezekiel 13:3-9 NASB)
Fulfilled Predictions ... Mark of a True Prophet of God?
Adventist.org goes on to say
The proof of a true prophet lies, in part, in the fulfillment of his/her predictions. Although Ellen White's work did not primarily consist of predicting the future, she did make a number of predictions that have been fulfilled in a remarkable way. 
Deuteronomy 18 is often quoted in the context of judging who is, or who isn't, a false prophet. However, one needs to read the words very carefully since, contrary to popular opinion, they do not say that a true prophet is one whose words come to pass. Verses 20-22 are very clear - any prophet whose predictions do not come true is a false prophet.
But the prophet who shall speak a word presumptuously in My name which I have not commanded him to speak, or which he shall speak in the name of other gods, that prophet shall die.’ And you may say in your heart, 'How shall we know the word which the Lord has not spoken?’ When a prophet speaks in the name of the Lord, if the thing does not come about or come true, that is the thing which the Lord has not spoken. The prophet has spoken it presumptuously; you shall not be afraid of him" (Deuteronomy 18:20-22).
Correctly predicting a future event does not prove someone to be a prophet of God - with good reason. Some people may be extremely astute at reading which way the wind is blowing. Predictions can also come true by chance or sheer luck. Since God makes no mistakes about the future, even one failed prediction, tells us that the prophet is not from God and we can safely ignore him or her.
However, the site ellenwhite.org says
On the larger question of whether a prophecy delivered by a genuine prophet of God ever may fail to come true, we must see what the *whole* Bible says about it, not just lean on one passage. Jeremiah 18:1-10 is instructive here, for the Bible makes it explicit that even after God has delivered His pronouncement of judgment or blessing (through one of His prophets), He may change it if circumstances call for it. This is illustrated clearly in the Book of Jonah. 
I am afraid that I find this explanation absolutely ludicrous.
In Jeremiah chapter 18, the prophet was sent down to the potter's house where he was making something on his wheel. However, the vessel he was attempting to form was "spoiled" and he remade it into another - a common enough occurrence with potters. This may appear to indicate that the Lord can change His mind regarding judgment or blessing if, as the site ellenwhite.org says, "circumstances call for it".
"Circumstances?" What circumstances can cause God to change His mind regarding judgment or blessing? Note very carefully what the Lord then said to Jeremiah...
"Can I not, O house of Israel, deal with you as this potter does?" declares the Lord. "Behold, like the clay in the potter's hand, so are you in My hand, O house of Israel. "At one moment I might speak concerning a nation or concerning a kingdom to uproot, to pull down, or to destroy it; if that nation against which I have spoken turns from its evil, I will relent concerning the calamity I planned to bring on it. "Or at another moment I might speak concerning a nation or concerning a kingdom to build up or to plant it; if it does evil in My sight by not obeying My voice, then I will think better of the good with which I had promised to bless it. (Jeremiah 18:6-10 NASB)
The punishment for sin and the rewards for righteousness is the warp and weft of the fabric of the Scriptures - the overriding theme in both Testaments. Therefore it stands to reason that every single one of God's pronouncements of judgment or blessing was strictly based on whether the person (or persons) concerned were obeying or disregarding His laws. These certainly are prophecies, but they are what is called "conditional prophecies" - solely predicated on a person's obedience or disobedience to the law. Every other type of prophecy is non-conditional. As the prophet Ezekiel said
"But if the wicked man turns from all his sins which he has committed and observes all My statutes and practices justice and righteousness, he shall surely live; he shall not die... But when a righteous man turns away from his righteousness, commits iniquity and does according to all the abominations that a wicked man does, will he live? All his righteous deeds which he has done will not be remembered for his treachery which he has committed and his sin which he has committed; for them he will die. (Ezekiel 18:21, 24 NASB)
The best known example of an explicitly stated conditional prophecy is the well known verse 2 Chronicles 7:14, which reads
If my people, which are called by my name, shall humble themselves, and pray, and seek my face, and turn from their wicked ways; then will I hear from heaven, and will forgive their sin, and will heal their land.
An implied warning is found in the book of Jonah. When he was sent to proclaim to the Assyrians that "Yet forty days and Nineveh will be overthrown", the point wasn't to tell the people that they would be destroyed in a few days, but to give them a period of time in which to repent.
Let me repeat again - Every type of prophecy other than those predicated on a person's obedience or disobedience to God's laws is non-conditional
Ellen White's False Prophecies
Some people quite close to Ellen White testified to some of her predictions as to the exact date of the Second Advent. However, although this evidence is widely disputed, there is still the matter of her several other failed predictions. These are just two of the many false predictions Ellen White made.
If the Lord didn't hasten His return, the earth would soon be depopulated
I was shown that many drive Christ from their families by an impatient, passionate spirit. Such have something to overcome in this respect. The human family was presented before me, enfeebled. Every generation has been growing weaker; and disease of every form visits the human race. Thousands of poor mortals are dragging out a miserable existence. Some with deformed, sickly bodies, shattered nerves, and gloomy minds. Satan's power upon the human family increases. If the Lord should not soon come and destroy his power, the earth would soon be depopulated. 
In 1850, there were an estimated 1.2 billion people on earth. Most people now live much longer thanks to better nutrition, living conditions, sanitation and advances in medicine. According to the United Nations, the world population reached 7 Billion on October 31, 2011. 
Slavery would be revived in the South
Slavery will again be revived in the Southern States; for the spirit of slavery still lives. Therefore it will not do for those who labor among the colored people to preach the truth as boldly and openly as they would be free to do in other places. Even Christ clothed His lessons in figures and parables to avoid the opposition of the Pharisees. When the colored people feel that they have the word of God in regard to the Sabbath question, and the sanction of those who have brought them the truth, some who are impulsive will take the opportunity to defy the Sunday laws, and by a presumptuous defiance of their oppressors they will bring to themselves much sorrow. Very faithfully the colored people must be instructed to be like Christ, to patiently suffer wrongs, that they may help their fellow men to see the light of truth. 
As a by the way, Jesus did not use parables to avoid the opposition of the Pharisees. The word parable comes from the Greek parabole, which means a likeness, illustration, or comparison. In other words, a parable is a short and simple story, generally featuring human characters, that uses the familiar to illustrate a spiritual point. Although parables are often colorful and easily remembered, the ones told by Jesus meant nothing to those who's hearts were hardened, because they required the listeners to realize that the story was about them. The Pharisees were anything but self critical, nor were they willing to learn, therefore they, as Jesus told them, heard but never understood, saw but never perceived.
Predictions Regarding The Timing of The End of Days and Jesus' Return
Because SDA theology teaches that Jesus will return as soon as He is done with the Investigative Judgment, these two categories are closely related.
A) The Timing of Jesus' Return
As far back as November 1848, Ellen White was apparently shown in a vision that Jesus was nearly finished in the Most Holy Place.
1848 "The time of trouble has commenced, it is begun. The reason why the four winds have not let go, is because the saints are not all sealed. It's on the increase, and will increase more and more; the trouble will never end until the earth is rid of the wicked... Why they are just ready to blow. There's a check put on because the saints are not sealed.” 
Two and a half months later, she wrote
1849: "The sealing time is very short, and soon will be over. Now is the time to make our calling and election sure, while the four angels are holding the four winds" 
However, even on this very important subject, Ellen White contradicted herself.
In the first line of the 1848 quote EW's use of the word "all" ("the saints are not all sealed") indicates that some of the people of God had already been sealed, i.e. the sealing was in progress.
We know that the word 'all' wasn't inadvertently inserted (a "typo") because, in an 1850 letter of consolation to the family of a woman who had died, Ellen White said "God gave me a view last Sabbath night which I will write. I saw that she was sealed and would come up at the voice of God and stand upon the earth, and would be with the 144,000." 
However, on page 605 of the 1888 version, of her book The Great Controversy, Ellen White wrote of the sealing as being in the future.
The Sabbath will be the great test of loyalty; for it is the point of truth especially controverted. When the final test shall be brought to bear upon men, then the line of distinction will be drawn between those who serve God and those who serve him not.... While one class, by accepting the sign of submission to earthly powers, receive the mark of the beast, the other, choosing the token of allegiance to divine authority, receive the seal of God. 
1849: I saw that the time for Jesus to be in the most holy place was nearly finished and that time can last but a very little longer. 
1850: A Vision the Lord Gave Me in Oswego, July 29, 1850.
Said the angel, Jesus' work is almost finished in the sanctuary. It is no time to be stupid now; a quick work will the Lord do upon the earth, the four angels will soon let go the four winds. 
The quotes above date back to 1849/1850. Yet, more than 40 years later, Ellen White wrote that Jesus
"... is today standing at the altar of incense, presenting before God the prayers of those who desire His help. 
The altar of incense was in the Holy Place, not the most Holy Place behind the veil - as Exodus 30 shows (Emphasis Added)
"Moreover, you shall make an altar as a place for burning incense; you shall make it of acacia wood ...You shall put this altar in front of the veil that is near the ark of the testimony, in front of the mercy seat that is over the ark of the testimony, where I will meet with you. (Exodus 30:1, 6 NASB)
And Ellen White knew full well where the altar of incense was. In a letter to Joseph Bates dated April 7, 1847, she wrote (Emphasis Added)
I saw an angel swiftly flying to me. He quickly carried me from the earth to the Holy City. In the city I saw a temple, which I entered. I passed through a door before I came to the first veil. This veil was raised, and I passed into the holy place. I saw the altar of incense, the candlestick with seven lamps, and the table on which was the shewbread, et cetera. After viewing the glory of the holy, Jesus raised the second veil, and I passed into the Holy of Holies. 
Apparently, Jesus was bouncing back and forth between the Holy Place and The Holy of Holies.
B) The Timing of The End of Days
Ellen White usually used the words soon, almost, and nearly finished in regard to Jesus' supposed work in the sanctuary. This was not an unknown concept in the New Testament. In fact, some have criticized Paul because, on several occasions he, using different expressions, said the time was short. For example,
The night is almost gone, and the day is near. Therefore let us lay aside the deeds of darkness and put on the armor of light. (Romans 13:12 NASB)
But this I say, brethren, the time has been shortened, so that from now on those who have wives should be as though they had none; (1 Corinthians 7:29 NASB)
However, this is no different from Jesus who told Christians in all ages to constantly anticipate His return and be ready at all times. In His words, "For this reason you also must be ready; for the Son of Man is coming at an hour when you do not think He will. (Matthew 24:44 NASB).
Paul very possibly thought the Second Coming could be around the corner and thus kept warning the newly formed church to be ready. However, he never once said, nor implied, that he knew when it would happen. Let us not forget that the apostle also stated that he did not know if he and the people he was writing to would be alive or dead when the Lord returned.
who died for us, so that whether we are awake or asleep, we will live together with Him. (1 Thessalonians 5:10 NASB)
And that certain events had to take place first.
that you not be quickly shaken from your composure or be disturbed either by a spirit or a message or a letter as if from us, to the effect that the day of the Lord has come. Let no one in any way deceive you, for it will not come unless the apostasy comes first, and the man of lawlessness is revealed, the son of destruction, (2 Thessalonians 2:2-3 NASB)
However, Ellen White made both general and very specific statements that indicated her belief that the end would come in the lifetime of her generation.
In 1849, a cholera epidemic once again reared its ugly head in the United States, largely because people had learned nothing about its prevention from the previous 1832 outbreak. Ellen White predicted that it would get much worse. In her words (Emphasis Added)
"What we have seen and heard of the pestilence, is but the beginning of what we shall see and hear. Soon the dead and dying will be all around us. I saw that some will be so hardened, as to even make sport of the judgments of God. Then the slain of the Lord will be from one end of the earth, to the other; they will not be lamented, gathered, nor buried; but their ill savor will come up from the face of the whole earth. Those only who have the seal of the living God, will be sheltered from the storm of wrath, that will soon fall on the heads of those who have rejected the truth" 
Because, in the preceding two paragraphs, Ellen White wrote of Christ still being in his Holy Temple and spoke of Him leaving the Sanctuary in the future tense, Seventh Day Adventists say that it is "abundantly clear that Ellen White believed the commencement of the final crisis was still future." 
No, it doesn't.
The word "beginning" signifies the point in time at which something starts. No matter how you try to spin it, Ellen White could not have used the word "beginning" if she believed the cholera plague was unrelated to the final crisis. Besides which, she said "what we have seen and heard" is the beginning of what "we" shall see, i.e. the dead will be all around "us".
Finally, if read in context, Ellen white wrote that souls must be rescued from the coming storm of wrath before Jesus leaves the Most Holy Place. The very next line says that the Lord showed her that precious souls were starving, and dying for want of truth and that messengers should speed to them "for the case of every soul will soon be decided, either for Life, or for Death.” 
The implication is very clear - the messengers should hurry with the message before Jesus left the most Holy Place. In support of this she also wrote (I believe in 1862)...
I saw that God's people must take warning and discern the signs of the times. The signs of Christ's coming are too plain to be doubted; and in view of these things every one who professes the truth should be living preachers. God calls upon all to awake; preachers and people must awake. All Heaven is astir. The scenes of this earth's history are fast closing. We are amid the perils of the last days. Greater perils are before us, and yet we are not awake. 
Signs In The Sun, And In The Moon, And In The Stars
Towards the end of His time on earth, Jesus was sitting on the Mount of Olive when He was asked by His disciples what the sign of His coming and the end of the age would be. His Olivet Discourse, as it is popularly known, was recorded by three of the evangelists. While Luke merely says "there will be signs in sun and moon and stars" (Luke 21:25), Matthew and Mark's accounts are virtually identical.
But in those days, after that tribulation, the sun will be darkened and the moon will not give its light, and the stars will be falling from heaven, and the powers that are in the heavens will be shaken. "Then they will see the Son Of Man coming in clouds with great power and glory. (Mark 13:24-26 NASB) Also See Matthew 24:29-30
John also spoke about a darkened sun and falling stars in Revelation 6:12. However, he added an earthquake to the list, saying that when Jesus "broke the sixth seal, and there was a great earthquake; and the sun became black as sackcloth made of hair, and the whole moon became like blood; and the stars of the sky fell to the earth, as a fig tree casts its unripe figs when shaken by a great wind. (Revelation 6:12-13 NASB)
In The Great Controversy, Ellen White linked at least three natural occurrences to Mark and John's signs of Jesus' coming. According to her, the first two signs occurred in the form of the 1755 Lisbon earthquake and the 'Dark Day' of 1780. See Footnote II. The third occurred in 1833, 50 years after the Lisbon earthquake and some 80 years after the day the sun was darkened for a while.
In 1833, two years after Miller began to present in public the evidences of Christ's soon coming, the last of the signs appeared which were promised by the Saviour as tokens of his second advent. Said Jesus, "The stars shall fall from heaven.” [Matthew 24:29.] And John in the Revelation declared, as he beheld in vision the scenes that herald the day of God: "The stars of heaven fell unto the earth, even as a fig-tree casteth her untimely figs, when she is shaken of a mighty wind.” [Revelation 6:13.] This prophecy received a striking and impressive fulfillment in the great meteoric shower of November 13, 1833. That was the most extensive and wonderful display of falling stars which has ever been recorded... " 
Explicit Statements About How Short Time Was
Ellen White also made some other even more explicit statements about how short she believed the time was. (All underlining mine)
People had to get ready in a few months: (Underlining added. Italics in original)
Some of us have had time to get the truth and to advance step by step, and every step we have taken has given us strength to take the next. But now time is almost finished, and what we have been years learning, they will have to learn in a few months. They will also have much to unlearn and much to learn again. 
Since the world was about to come to an end, there was no point in getting married.
In this age of the world, as the scenes of earth's history are soon to close and we are about to enter upon the time of trouble such as never was, the fewer the marriages contracted, the better for all, both men and women. 
Children may never enter college
Because time is short, we should work with diligence and double energy. Our children may never enter college... 
Some of those who were then alive would hear the trump of God
The hour will come; it is not far distant, and some of us who now believe will be alive upon the earth, and shall see the prediction verified, and hear the voice of the archangel, and the trump of God echo from mountain and plain and sea, to the uttermost parts of the earth. 
Food For Worms
Perhaps the most noteworthy of all was a specific prophecy made at a conference held at Battle Creek in May, 1856, and later published in her Testimonies to the Church. At the conference, Ellen White said that in a vision given to her, she saw that some of those alive at the time would either become worm food or be translated to heaven without seeing death. I believe (but could be wrong) that this was the last time Ellen White made a specific prophecy regarding Christ's return.
A Conference was held at Battle Creek in May, 1856... At the conference a very solemn vision was given me. I saw that some of those present would be food for worms, some subjects for the seven last plagues, and some would be translated to heaven at the second coming of Christ, without seeing death. 
Note that this was supposedly supplied in a "solemn vision". So what are we to make of the fact that none of those people at the 1856 conference did not see death but were "translated to heaven at the second coming of Christ"? Again...
"When a prophet speaks in the name of the Lord, if the thing does not come about or come true, that is the thing which the Lord has not spoken. (Deuteronomy 18:22 NASB)
Behold, I am against the prophets," declares the Lord, "who use their tongues and declare, 'The Lord declares.' "Behold, I am against those who have prophesied false dreams," declares the Lord, "and related them and led My people astray by their falsehoods and reckless boasting; yet I did not send them or command them, nor do they furnish this people the slightest benefit," declares the Lord. (Jeremiah 23:31-32 NASB)
Is The Timing of Jesus' Return Conditional?
Ellen White wrote the following in 1883, more than 30 years after she said Jesus' work was almost finished in the sanctuary which, if you recall, she said the Lord had showed her..
As the subject was presented before me, the period of Christ's ministration seemed almost accomplished. Am I accused of falsehood because time has continued longer than my testimony seemed to indicate? How is it with the testimonies of Christ and His disciples? Were they deceived?" 
She then went on to quote several New Testament verses (Romans 13:12, 1 Corinthians 7:29, Revelation 1:3 and 22:6-7) all of which mention time as being short, which is certainly true and has been dealt with above. However, in the next few paragraphs, Ellen White wrote that had people done what they were supposed to have done, Christ would have returned. (Emphasis Added)
The angels of God in their messages to men represent time as very short. Thus it has always been presented to me. It is true that time has continued longer than we expected in the early days of this message. Our Saviour did not appear as soon as we hoped. But has the word of the Lord failed? Never! It should be remembered that the promises and threatening of God are alike conditional.
God had committed to His people a work to be accomplished on earth... Had Adventists, after the great disappointment in 1844, held fast their faith, and followed on unitedly in the opening providence of God, receiving the message of the third angel and in the power of the Holy Spirit proclaiming it to the world, they would have seen the salvation of God, the Lord would have wrought mightily with their efforts, the work would have been completed, and Christ would have come ere this to receive His people to their reward. 
However, the million dollar question is whether there are any conditions attached to Jesus' return.
Acts 17:31 says God has
"fixed (Gk. histemi) a day in which He will judge the world in righteousness through a Man whom He has appointed, having furnished proof to all men by raising Him from the dead." (NASB)
The Greek word translated 'fixed' is the verb histemi which means "to cause or make to stand, to place, put, set (Thayer). In other words, although God has not revealed it to man, the date He will judge the world is set in stone.
Besides which, as previously mentioned, a series of events has to take place before Jesus' second advent. When he heard that the Thessalonians feared that they had missed the rapture, Paul wrote them a comforting letter reminding them of what had to happen before the coming of the Lord. In his words...
Let no one in any way deceive you, for it will not come unless the apostasy comes first, and the man of lawlessness is revealed, the son of destruction, who opposes and exalts himself above every so-called god or object of worship, so that he takes his seat in the temple of God, displaying himself as being God. (2 Thessalonians 2:3-4 NASB)
The order being
1) The great apostasy or falling away (which, by the way, is already here).
2) The restrainer is taken out of the way (V. 6-7).
3) The man of sin/the rider on the white horse/the antichrist is revealed.
I strongly suggest you read End of The Age Not only does the imagery and symbolism of Revelation describe the horrendous conditions of the last days, but tells us in what order they will occur.
(Incidentally, Peter's words... "with the Lord one day is like a thousand years" simply means that the seven days of creation symbolize the seven thousand years of human history... from the days of Adam to the end of this era - See The Sabbath Millennium
[PLACE IN TEXT]
Footnote I. Ellen's White's 2,000 visions.
This estimate was made by Arthur White, who said
Through the 70 years of her ministry to the Adventist Church and the world, Ellen White closely tied in to the work of the Holy Spirit--so closely that the Spirit gave her 2,000 visions. [a]
A plaque at Oak Hill Cemetery Battle Creek where the Whites are buried, says the same thing. [b]
James White, on the other hand, said
She has probably had, during the past twenty-three years, between one and two hundred visions. Life Incidents p. 272. [c]
"There was a great earthquake"... The 1755 Lisbon earthquake?
Prophecy not only foretells the manner and object of Christ's coming, but presents tokens by which men are to know when it is near. Said Jesus: "There shall be signs in the sun, and in the moon, and in the stars." [Luke 21:25.] "The sun shall be darkened, and the moon shall not give her light, and the stars of heaven shall fall, and the powers that are in heaven shall be shaken. And then shall they see the Son of man coming in the clouds with great power and glory." [Mark 13:24-26.] The Revelator thus describes the first of the signs to precede the second advent: "There was a great earthquake; and the sun became black as sackcloth of hair, and the moon become as blood.” [Revelation 6:12.]
These signs were witnessed before the opening of the present century. In fulfillment of this prophecy there occurred, in the year 1755, the most terrible earthquake that has ever been recorded. Though commonly known as the earthquake of Lisbon, it extended to the greater part of Europe, Africa, and America. It was felt in Greenland, in the West Indies, in the island of Madeira, in Norway and Sweden, Great Britain and Ireland. [d]
The 1755 Lisbon earthquake, also known as the Great Lisbon earthquake, occurred at around 09:40 local time on All Saints' Day in the Kingdom of Portugal. In combination with subsequent fires and a tsunami, the earthquake almost totally destroyed Lisbon and adjoining areas. Seismologists today estimate the Lisbon earthquake had a magnitude in the range 8.5–9.0 . As terrible as this was, the 2004 Sumatra, Indonesia earthquake registered 9.1 to 9.3 on the Richter scale, caused some five tsunamis, and killed around 200,000 people.
See Deadliest earthquakes on record. [e]
"The Sun Shall Be Darkened"... The 'Dark Day' of 1780?
In the Saviour's conversation with his disciples upon Olivet, after describing the long period of trial for the church - the 1260 years of papal persecution, concerning which he had promised that the tribulation should be shortened - he thus mentioned certain events to precede his coming, and fixed the time when the first of these should be witnessed: "In those days, after that tribulation, the sun shall be darkened, and the moon shall not give her light.” [Mark 13:24.] The 1260 days, or years, terminated in 1798. A quarter of a century earlier, persecution had almost wholly ceased. Between these two dates, according to the words of Christ, the sun was to be darkened. On the 19th of May, 1780, this prophecy was fulfilled. [f]
As a by the way, for the past 200 + years historians and scientists have argued over the origins of the Dark Day, as it is popularly called, that occurred on May 19, 1780 in New England and parts of eastern Canada. However, many scientists, having "found signs of fire-scarred rings in tree trunks dating back to that period" assume the darkness was due to a forest fire. Numerous other "dark days" have been recorded - One that occurred in North America in 1950 was caused by forest fires in Alberta, Canada.  [PLACE IN TEXT]
End Notes. Was Ellen White a True Prophetess of God?
 Ellen G. White Writings. Ellen White. Selected Messages Book 1.
 Ellen G. White Writings. Ellen White. Messenger to the Remnant, Page 125. Chapter 9—God's Messenger
 Ellen G. White Writings. Ellen White. From the Heart, Page 3.
 Ellen G. White Writings. Ellen White. The Review and Herald. June 9, 1885.
 Ellen G. White Writings. Ellen White. The Great Controversy 1888, Page g.
 Ellen G. White Writings. Ellen White. Selected Messages Book 1, Page 27.
 Ellen G. White Writings. Ellen White. Lt 339, 1904.
 Ellen G. White Writings. Ellen White. Testimony for the Battle Creek Church, Page 46-49
 The Seventh day Adventist church of UK and Ireland. More Answers http://adventist.org.uk/who-we-are/what-we-believe/fundamentals/3
 28 Fundamental Beliefs https://www.adventist.org/fileadmin/adventist.org
 Ellen G. White Writings. Ellen White. Lt 329, 1905.
 Ellen G. White Writings. Ellen White. The Review and Herald. May 25, 1905.
 The Gift of Prophecy.. https://www.adventist.org/en/spirituality/prophecy/article/go/-/the-gift-of-prophecy/
 Seventh Day Adventist. The Gift of Prophecy.
 Ellen G. White: Ellen White. The Early Years: 1827-1862 (vol. 1), Page 123.
 Seventh Day Adventist. The Gift of Prophecy. Testing a Prophet. h
 Failed Prediction http://ellenwhite.org/content/file/failed-prediction#document.
 Ellen G. White Writings. Ellen White. Testimony for the Church. The Review and Herald. April 22, 1862.
 World Population Milestones http://www.worldometers.info/world-population/
 Ellen G. White Writings. MR No. 153—Statement Concerning Slavery. Manuscript Releases, vol. 2 [Nos. 97-161.
 Ellen G. White Writings. Report of E. G. White Utterances During Vision, November 19, 1848
 Ellen G. White Writings. Ellen White. To Those who are receiving the seal of the living God. January 31, 1849
 Ellen G. White Writings. Ellen White. Words to Husband and Children on the Loss of Wife and Mother.
 Ellen G. White Writings. Ellen White. The Great Controversy 1888, Page 605.
 Ellen G. White Writings. Ellen White. The Present Truth. September 1, 1849
 Ellen G. White Writings. Ellen White. Ms 5, 1850.
 Ellen G. White Writings. Ellen White. Daughters of God, Page 240. http://text.egwwritings.org/publication.php?pubtype=Book&bookCode=DG&pagenumber=240
 Ellen G. White Writings. Ellen White: The Early Years: 1827-1862 (vol. 1), Page 120.
 Ellen G. White Writings. Ellen White. Present Truth, Sept. 1849.
 Jud Lake, Pestilence Prophecy. http://www.ellenwhiteanswers.org/media/pdf/ellen-white-pestilence-prophecy.pdf
 Ellen G. White Writings. Ellen White. Present Truth, Sept. 1849.
 Ellen G. White Writings. Ellen White. Chapter 7—Great Distress Coming, and God's People Not Prepared For It.
Ellen G. White Writings. Ellen White. The Great Controversy 1888, Page 332-333.
 Ellen White. Early Writings, Page 67. http://text.egwwritings.org/publication.php?
 Ellen G. White Writings. Ellen White. Testimonies for the Church, vol. 5, Page 366.
 Ellen G. White Writings. Ellen White. Testimonies for the Church, vol. 3, Page 159.
 Ellen G. White Writings. Ellen White. The Review and Herald. July 31, 1888.
 Ellen G. White Writings. Ellen White. Life Sketches of James White and Ellen G. White 1880, Page 321.
 Ellen G. White Writings. Ellen White. Ms 4, 1883. "An Unreasonable Conjecture".
 Ellen G. White Writings. Ms 4, 1883. "Time Nearly Finished".
[a] Arthur L. White. Charismatic Experiences In Early Seventh-Day Adventist History.
SDA's and Ecstatic Experiences--6. Ellen G. White and the Baptism of the Holy Spirit.
[c] Ellen G. White Writings. Ellen White: The Early Years: 1827-1862 (vol. 1), Page 123.
[d] Ellen G. White Writings. Ellen White The Great Controversy 1888, Page 304.
[f] Ellen G. White Writings. Ellen White. The Great Controversy 1888, Page 306.
[g] Tom de Castella. What caused the mystery of the Dark Day?. http://www.bbc.com/news/magazine-18097177