So from what you have written, her writings on not on a par w scripture?
If so, then they are in no way binding, nor needed for anyone
May these help you understand, even as it was in the OT and the NT times, on why Isaiah was sent, and Jeremiah, and Daniel, and Paul, and so many others, in addition to the Law of God (the Ten Commandments):
You can see much here, on why the Testimonies were given through sister White -
Why:
"... I took the precious Bible and surrounded it with the several Testimonies for the Church, given for the people of God. Here, said I, the cases of nearly all are met. The sins they are to shun are pointed out. The counsel that they desire can be found here, given for other cases situated similarly to themselves. God has been pleased to give you line upon line and precept upon precept. But there are not many of you that really know what is contained in the Testimonies. You are not familiar with the Scriptures. If you had made God's word your study, with a desire to reach the Bible standard and attain to Christian perfection, you would not have needed the Testimonies. It is because you have neglected to acquaint yourselves with God's inspired Book that He has sought to reach you by simple, direct testimonies, calling your attention to the words of inspiration which you had neglected to obey, and urging you to fashion your lives in accordance with its pure and elevated teachings. {2T 605.1}
The Lord designs to warn you, to reprove, to counsel, through the testimonies given, and to impress your minds with the importance of the truth of His word. The written testimonies are not to give new light, but to impress vividly upon the heart the truths of inspiration already revealed. Man's duty to God and to his fellow man has been distinctly specified in God's word; yet but few of you are obedient to the light given. Additional truth is not brought out; but God has through the Testimonies simplified the great truths already given and in His own chosen way brought them before the people to awaken and impress the mind with them, that all may be left without excuse. {2T 605.2} ..."
Notice:
"... I recommend to you, dear reader, the Word of God as the rule of your faith and practice. By that Word we are to be judged. God has, in that Word, promised to give visions in the "last days"; not for a new rule of faith, but for the comfort of His people, and to correct those who err from Bible truth. Thus God dealt with Peter when He was about to send him to preach to the Gentiles. (Acts 10.) {EW 78.1} ..."
Again:
"... When God's Word is studied, comprehended, and obeyed, a bright light will be reflected to the world; new truths, received and acted upon, will bind us in strong bonds to Jesus. The Bible, and the Bible alone, is to be our creed, the sole bond of union; all who bow to this Holy Word will be in harmony. Our own views and ideas must not control our efforts. Man is fallible, but God's Word is infallible. Instead of wrangling with one another, let men exalt the Lord. Let us meet all opposition as did our Master, saying, “It is written.” Let us lift up the banner on which is inscribed, The Bible our rule of faith and discipline.—The Review and Herald, December 15, 1885.... {1SM 416.2}"
Again:
"... It is not enough to merely profess to believe the truth. All the soldiers of the cross of Christ virtually obligate themselves to enter a crusade against the adversary of souls, to condemn wrong, and sustain righteousness. But the message of the True Witness reveals the fact that a terrible deception is upon our people, which makes it necessary to come to them with warnings, to break their spiritual slumber, and arouse them to decided action. {RH, September 16, 1873 par. 8}
This message of the True Witness has not accomplished the design of God. The people slumber on in their sins. They continue to declare themselves "rich, and having need of nothing." Many inquire, Why are all these reproofs given? Why do the testimonies continually charge us with backsliding and grievous sins? We love the truth. We are prospering. We are in no need of these testimonies of warning and reproof. But let these murmurers see their hearts, and compare their lives with the practical teachings of the Bible; let them humble their souls before God; let the grace of God illuminate the darkness, and the scales will fall from their eyes, and they will sense their true spiritual poverty and wretchedness. They will feel the necessity of buying gold, which is pure faith and love; white raiment, which is a spotless character, made pure in the blood of their dear Redeemer, and eye-salve, which is the grace of God, and will give clear discernment of spiritual things, and detect sin. These attainments are more precious than the gold of Ophir. {RH, September 16, 1873 par. 9}
I am very sure that the greatest reason why the people of God are now found in this state of spiritual blindness, is because they will not receive correction. Many have despised the reproofs and warnings given them. The True Witness condemns the lukewarm condition of the people of God, which gives Satan great power over them in this waiting, watching time. The selfish, and proud, and lovers of sin, are ever assailed with doubts. Satan has ability to suggest doubts and devise objections to the pointed testimony that God sends, and many think it a virtue and mark of intelligence in them to be unbelieving and questioning, and quibbling. Those who desire to doubt will have plenty of room. God does not propose to remove all occasion for unbelief. He gives evidence, which must be carefully investigated with a humble mind and teachable spirit. All should decide from the weight of evidence. {RH, September 16, 1873 par. 10} ..."
Another:
"... Why do we need a Matthew, a Mark, a Luke, a John, a Paul, and all these other writers who have borne their testimony in regard to the life of the Saviour during His earthly ministry? Why could not one of the disciples have written a complete record, and thus have given us a connected account of Christ's life and work? The Gospels differ. One writer brings in points that another does not bring in. If these points are essential, why did not all these writers mention them? It is because the minds of men differ, and do not comprehend all things in exactly the same way. Some Scripture truths appeal much more strongly to the minds of certain persons than to others; some points appear to be much more important to some than to others. The same principle applies to speakers. Some speakers dwell at considerable length on points that others would pass by quickly, or not mention at all. Thus the whole truth is presented more clearly by several than by one. In the Gospels the records blend in one harmonious whole. {2SAT 241.3} ..."