To what degree did Ellen White influence the formation of Seventh-day Adventist doctrine?
This question is easy to answer. Ellen White answers this question for us in the following four passages:
Our first conference was at Volney in Bro. Arnold's barn. There were about thirty-five present, all that could be collected in that part of the State. There were hardly two agreed. Each was strenuous for his views, declaring that they were according to the Bible. All were anxious for an opportunity to advance their sentiments, or to preach to us. They were told that we had not
come so great a distance to hear them, but had come to teach them the truth. Bro. Arnold held that the 1000 years of Rev. xx were in the past; and that the 144,000 were those raised at Christ's resurrection. And as we had the emblem of our dying Lord before us, and was about to commemorate his
sufferings, Bro. A. arose and said he had no faith in what we were about to do; that the Sacrament was a continuation of the Passover, to be observed but once a year. These strange differences of opinion rolled a heavy weight upon me, especially as Bro. A. spoke of the 1000 years being in the past. I knew that he was in error, and great grief pressed my spirits; for it seemed to me that God was dishonored. I fainted under the burden. Brethren
Bates, Chamberlain, Gurney, Edson, and my husband, prayed for me. Some feared I was dying. But the Lord heard the prayers of his servants, and I revived. The light of Heaven rested upon me. I was soon lost to earthly things. My accompanying angel presented before me some of the errors of those present, and also the truth in contrast with their errors. That these discordant
views, which they claimed to be according to the Bible, were only according to their opinion of the Bible, and that their errors must be yielded, and they unite upon the third angel's message. Our meeting ended victoriously. Truth gained the victory. Spiritual Gifts. Volume 2, pp. 97-99
At that time [after the 1844 disappointment] one error after another pressed in upon us; ministers and doctors brought in new doctrines. We would search the Scriptures with much prayer, and the Holy Spirit would bring the truth to our minds. Sometimes whole nights would be devoted to searching the Scriptures and earnestly asking God for guidance. Companies of devoted men and women assembled for this purpose. The power of God would come upon me, and I was enabled clearly to define what is truth and what is error. As the points of our faith were thus established, our feet were placed upon a solid foundation. We accepted the truth point by point, under the demonstration of the Holy Spirit. I would be taken off in vision, and explanations would be given me. I was given illustrations of heavenly things, and of the sanctuary, so that we were placed where light was shining on us in clear, distinct rays. Selected Messages Book 3, pp. 31, 32
Let none seek to tear away the foundations of our faith,--the foundations that were laid at the beginning of our work, by prayerful study of the Word and by revelation . . . .Gospel Workers. 1915 ed., p. 307
At this time . . . Serious errors in doctrine and practice were cherished, and some were ready to condemn all who would not accept their views. God revealed these errors to me in vision and sent me to His erring children to declare them . . . Testimonies for the Church Volume Five,
p. 655, 656

Seventh-day Adventists acknowledge the influence of Ellen White in the definition of their doctrines, but insist that she is a light pointing us to the Bible and not to herself as the final authority of truth. Further, we insist that every doctrine we uphold is supported by the Bible.