How can I confirm or disprove this statement.

Do a search on "inerrant" and then look at the hits in Adventist Today, an SDA journal. 

While they are not voted statements, they are reflective of the general church teaching on the matter.

There are the teachings of the church and then there are the members:

There are a range of Seventh-day Adventist thoughts on Ellen G. White
From any given Bible text many sermons could be given as different parts of the texts are emphasized.

There are some that do not accept Ellen G. White as a prophet.
They don’t care what she said on a subject.

Others look to her for her guidance and study her conclusions rather than her every word.
They see her readings and conclusions as true guidance but not the last word. But they also see other sermons in that text and they see that those other readings do not take away from her readings.

But there are others who cling to her every word as coming straight from the mouth of God.
They see her reading of the text as the only one there can be.

For example: there is one story [not a parable but a story] that she concludes means that we should not take our eyes off Jesus – a very true conclusion. A non-sister White telling of that story shows how God uses man as His agent. It sometimes becomes very difficult to show the other possible conclusions once “Sister White” has been seen to speak.

What were her thoughts on her words?
“”At the same time she emphasized her submission to the Bible, which she called “the greater light” (CM 125). “We are to receive God’s Word as supreme authority,” she wrote (6T 402). “The Holy Scriptures are to be accepted as an authoritative, infallible revelation of His will. They are the standard of character, the revealer of doctrines, and the test of experience” (GC vii). Therefore, she said, “the testimonies of Sister White should not be carried to the front. God’s Word is the unerring standard.… Let all prove their positions from the Scriptures and substantiate every point they claim as truth from the revealed Word of God” (Ev 256). At a meeting held in the Battle Creek College library on the eve of the General Conference of 1901 she told the leaders, “Lay Sister White right to one side.… Don’t … [ever] quote my words again as long as you live, until you can obey the Bible” (SpM 167).””
From Gerhard Pfandl, “Authority of Ellen G. White and Her Writings,” ed. Denis Fortin et al., The Ellen G. White Encyclopedia (Hagerstown, MD: Review and Herald Publishing Association, 2013), 628–629.

My reading of that is that she said that if one needs to quote her to prove a point that one has not gotten deep enough into the Bible.

But there are others who cling to her every word as coming straight from the mouth of God.

I may have too many books in my library. While continuing my research on Sister White of the SDA Church I found that there are others that see their leaders as more than their leaders see themselves.

“It’s natural to link papal mistakes with the issue of infallibility. We’ve already given a context that theoretically separates the pope as a man from the pope as the successor to St. Peter making an ex cathedra statement on a matter of faith and morals. In the common opinion of many, however, this is a distinction without a difference: most people do not separate the pope from every statement he utters despite the careful theology behind Vatican I and Vatican II teachings.”
Christopher M. Bellitto, 101 Questions & Answers on Popes and the Papacy (New York; Mahwah, NJ: Paulist Press, 2008), 93.

MJ.  What do you mean by regional and ethnic?

MJ, that sounds very much like the English Catholics that I am friendly with and also those that I know of. Very much like most of the old time SDAs in England as well. I can still hear the grunt "That is the American church". And as for varying attitudes (and practises) to the ordination of Women ministers throughout the world  . . . ..

In that sense the two groups have a lot in common in their attitudes to their respective 'head office's'. I am not sure if either side would appreciate that comment however [:D]  

But there are others who cling to her every word as coming straight from the mouth of God.

Fortunately, in the UK they are VERY much of a minority (2% ?) and because of that tend to meet together.much of the time 

Sorry that it took so long but I finally found this published statement on the work of EGW:

February 21, 1899

33rd Session. - WORCESTER, MASS., TUESDAY, - VOLUME 8. SOUTH LANCASTER, MASS. - NUMBER 5

The Daily Bulletin,

PUBLISHED BY THE GENERAL CONFERENCE OF
Seventh-day Adventists.

BIBLE STUDY. THE BOOKS OF DANIEL AND REVELATION.
Synopsis of Lesson by Elder A. T. Jones

If we would study the books of Daniel and Revelation, and the book of John, and the rest of the Bible, as we must in order to be Christians, we would not need to be told by the Lord that righteousness by faith is the third angel's message. If we would study the Bible as God calls us to study it, the Testimonies would not need to come to tell us so many things that we are ignorant of. Then we would not need to bolster up the Bible with the Testimonies. The Bible is enough, brethren. The only reason the Testimony comes is that we have not taken the Bible. We can not present the Testimonies to people who do not know anything about the Testimonies. We must preach the word of God. That has strength in it for all people. The prophecies are for those who believe, not for those who believe not. They are given to you and me to teach us, and we are to learn by them. But we are to learn by them what is in the Bible, and then preach that thing from the Bible, and not from the Testimonies. Now I do not think anybody will accuse me of not being loyal to the Testimonies. I hope not, anyhow. {February 21, 1899 N/A, GCDB 46.21}

General Conference Daily Bulletin, Vol. 8 (1899)

[[The Testimonies are nine books published by EGW that summarize her works.]]

Great timely quote David. I remember learning that one at seminary. I've enjoyed reading through this thread.