It sounds like she is in desperate need of help. If she is unwilling to get help and work on dealing with her past and abuse, then well there is nothing you can really do. You can't just stay with her because you fear she could harm herself, that's emotional blackmail.

Lots of people think Love can conquer all .. But that's just not really true. Sometimes love means taking care of yourself.

Are you seeing a Therapist? if not I think it would be smart for you to, You are going through terrible abuse from her. In sure you need to process this situation and find out what is going to be healthy for you.

I hope shes willing to reach out for help.