I am not an SDA but I find their doctrine closest to the Bible than any other religion. I don't agree with many things about them but those have nothing to do with their doctrine I have to say.
If you're talking about Ellen G White, as far I know she was one of the founders of the Church. She's the most well known because she was a prophetess. She does cause a lot of contention though and many have left the Adventist church because they don't believe she was a prophet of God.
Women can hold positions in Church just not in the same capacity as men. Women are not to be pastors or elders, because doing so would place them in a leadership role over men (1 Timothy 2:11–14; 1 Corinthians 14:34, 35), there are other things that women can and should do. Their ministry revolves around support, service, and ministry to women and children.
Throughout the Bible, women are shown in ministry. Several examples include Deborah, who was a judge of Israel (Judges 4:4); Huldah and Anna, who were prophetesses (2 Chronicles 34:22; Luke 2:36); Priscilla, who was active in evangelism (Acts 18:26); and Pheobe, who was a deaconess (Romans 16:1). So women have an incredibly important role in God’s Church throughout the ages.
No we are not commanded to be vegetarians. I have never read anywhere in SDA literature that we are commanded to be vegetarian. They know God allowed man to eat meat although He told us what meat we should and shouldn't eat. Rather they point out that in scripture we are told our bodies are to be the temple for the Holy Spirit (1 Corinthians 6:19-20). The Bible says in Romans 12:1, "I beseech you therefore, brethren, by the mercies of God, that ye present your bodies a living sacrifice, holy, acceptable unto God, which is your reasonable service." If we are to be living sacrifices , holy acceptable to God, we should present ourselves in as good condition as possible, avoiding habits, physical, mental or spiritual, which damage our minds and bodies. God is concerned about everything we do and asks us to do everything to His glory including what we eat and drink (1 Corinthians 10:31).
They talk about the original diet of man, when God added extra foods to our diets and why. When and why meat came into mankind's diet (the flood), and how it affected them. They also talk about clean and unclean animals that should be eaten. Daniel and his three friends showed that in only ten days they were healthier than the others who ate meat and wine. They ate essentially a vegan diet and proved that God's original diet is the right one. Daniel 1:8-16. I have a thread on this exact subject.
https://vigilantcitizenforums.com/threads/the-original-diet-of-mankind-and-the-old-testament-dietary-laws-do-they-still-apply.4467/.
The SDA's have many issues and are definitely not a perfect Church nor have I suggested they are but they believe in a thus says the Lord more than most Christian religions out there to the point some have called them legalists.
- They believe that all Christians should obey all the ten commandments including the fourth commandment about keeping the Sabbath. Most Christian religions keep the first day of the week not the Sabbath as God intended. I also have a thread on the subject.
https://vigilantcitizenforums.com/threads/who-changed-the-sabbath-day-from-saturday-to-sunday.4393/
- They believe God is particular about obedience, which He is. None of us can obey in our own power, but through Christ we can and must. Obedience is the fruit of a relationship with God. If we love him, we keep His commandments. John 14:15.
- They believe and teach about the the ministry of Christ in the heavenly sanctuary. Many Christian religions don't believe that but is biblical. I started a thread yesterday about that too. Many Christians are Zionists/dispensationalists and believe that an earthly temple is going to be rebuilt contrary to the word of God which clearly states that Jesus went back to heaven and is the High priest in the heavenly sanctuary. The book of Hebrews tells us more about the heavenly sanctuary.
- They believe and teach about spiritual gifts within the body of Christ. Spiritual gifts are given to a Christian by the Holy Spirit after they join the fellowship of believers or upon baptism. Just as when Jesus was baptized: by John, and the Spirit of God descended upon Him in the form of a dove, so anyone who is baptized by water is to also to receive the Spirit, for only with the presence of the Holy Spirit in a person’s life are they able to walk the Christian life. Spiritual gifts received upon baptism may be specialities that are already built on talents previously developed, or they may even be tendencies only discovered after an individual has given their life to Christ and is walking with Him. Christians are to use their spiritual gifts to in loving ministry for the common good of the church and of humanity. In 1 Corinthians 12 Paul explains about the gifts, what they are for ans how they are to be used. He talks about spiritual gifts in other parts of the New Testament too.
- They believe in the Second coming of Christ. Most Christians believe in Jesus' second coming but some have twisted how He will come and when contrary to what the Bible teaches. The Bible teaches that Jesus' second coming of Christ is the blessed hope of the church, the grand climax of the gospel. The Saviour’s coming will be literal, personal, visible, and worldwide. When He returns, the righteous dead will be resurrected, and together with the righteous living will be glorified and taken to heaven, but the unrighteous will die. The almost complete fulfilment of most lines of prophecy, together with the present condition of the world, indicates that Christ’s coming is imminent. The time of that event has not been revealed, and we are therefore exhorted to be ready at all times.
- They believe in the Millennium and the end of sin. The millennium is the thousand-year reign of Christ with His saints in heaven between the first and second resurrections. During this time the wicked dead will be judged; the earth will be utterly desolate, without living human inhabitants, but occupied by Satan and his angels. At its close Christ with His saints and the Holy City will descend from heaven to earth. The unrighteous dead will then be resurrected, and with Satan and his angels will surround the city; but fire from God will consume them and cleanse the earth. The universe will thus be freed of sin and sinners forever.
- They believe in the New Earth, in which righteousness dwells, God will provide an eternal home for the redeemed and a perfect environment for everlasting life, love, joy, and learning in His presence. For here God Himself will dwell with His people, and suffering and death will have passed away. The great controversy will be ended, and sin will be no more. All things, animate and inanimate, will declare that God is love; and He shall reign forever. Amen.
There are many more beliefs that are peculiar to them but they are all biblical. They believe as every Christian should that the Holy Scriptures, Old and New Testaments, are the written Word of God, given by divine inspiration through holy men of God who spoke and wrote as they were moved by the Holy Spirit. In this Word, God has committed to man the knowledge necessary for salvation. The Holy Scriptures are the supreme, authoritative, and the infallible revelation of His will. They are the standard of character, the test of experience, the definitive revealer of doctrines, and the trustworthy record of God’s acts in history.