The fact that you revealed she is a Mormon makes all the difference in the world. I was going to tear into you, instead, I see the deep problem you have encountered.
Was she raised Mormon? Were you? Did you have any agreement going into marriage as to which church you would attend and raise your children in?
If she was raised a Mormon, or is a long time member, you are going to have a hard time moving her. She is in a cult. All her friends are there, and her parents and family are Mormon, then she will feel like she suddenly is being torn apart from her church and religious beliefs. That is her security and stability. Plus, she may also believe that only Mormons are saved, so leaving that church would be like losing her salvation. I hope you can open your eyes and see what is happening from her perspective, even if everything she believes is totally wrong, which it is.
If you leave her, she might have to shun you and take your children away, or go into hiding with them. So carrying a big stick isn't going to work.
I agree with those who say start a Bible study at home. You can even compare and contrast the Book of Mormon with the Bible. I was given a BoM the second year I was a Christian. I had already read it twice, plus, I had memorized a lot of KJV as a child. It only took me a few pages to find conflicts between the 2 books, and return the BoM on their next visit. I am sure you can find a book that compares the 2, to prepare yourself. But, this study has to be done with love.
right now you are very angry. No, I don't blame you, but if you promised to attend the Mormon church with her, she may view your actions as outright bullying.
So, you made a commitment to her, love her as Eph 5 says a husband should love his wife as Christ loves the church. Make her feel special. Remember Christ not only suffered for us, he died for us. Can you show that kind of gracious love to your wife? The Bible commands it!
Become a prayer warrior, and pray her into the a kingdom of God. Witness in love, be incredibly gently when you have to correct her for her bad theology.
Mormons are not Christians, because they have so many doctrines not found in the Bible. It is a cult, for sure. But pray, witness and study the Bible. I witnessed and prayed for my dad for 31 years, and he was saved 5 months before he died. My sister got saved last year, 38 years after I started praying for her to be saved and prayed for God to open doors. She phoned me one day and started to tell me about her little a Baptist church. Even I had prayed for both of them, and my grandmother before me, I was shocked when God saved them. That was the whole point of my prayers.
Always remember that it is God who saves people. But God has called us to be witnesses, and show them the love and truth of Jesus Christ! God bless you as you begin to love your wife more, and pray for her. I will pray for you to have strength not to be angry or frustrated with her, but rather, win her with the Word of God, and love her with the same love God has for lost souls.
