What drives Mary Warren?

Why does Mary Warren take back her statement about the devils spirit being a fake?

Mary Warren is the servant at the Proctors house. She took over after Abigail, and tries to please mr. and mrs. Proctor in the best possible ways. She is a part of Abigail's group of young girls that accuses people for witchcraft. Proctor has seen through their games, and he is threatening Mary to tell the truth about what's really going on. Mary is terrified of Proctor, but at the same time Abigail has so much power that no one will step over her feet. Mary is brave and takes her statement to the judge. She soon learns that she has made a bad choice and the other girls now frame Mary for being in possession of the devil. The only wise thing Mary can do now is to turn to the girls and pretend that she actually was possessed, but has now turned to God. This is what Mary does, and John Proctor gets framed for being the devil as he pushed her to telling the truth to save his wife. 

I think this happens because Mary knows how much power Abigail has, and if she turns away from her, Mary is the only one that is going to pay for it. She tries to conquer her fear, but she fails. She knows not to lie and not to turn away from God, but she is too afraid of her own life to keep these promises. She is afraid of being hanged and afraid of what Abigail might do to her. 

So I mean that what drives Mary Warren is fear. First the fear of John Proctor, then the fear of ending her own life and last but not least the fear of what Abigail might do.