Feanor ... if she is being physically, verbally, and mentally abusive, as seems to have been described, that's unacceptable. Having repeatedly done this, its time to draw a line. Sometimes it is difficult for the person who is emotonionally involved with such a person to see what's happening, but it is seemingly happening in your situation. She is acting in a controling fashion and she needs to break her bad habits, or get some some help to be able to break them. If you can recognize that your own habit of trying to help her, isn't working that a good first step for yourself.
Sometimes folks like you and me (yes, I've been there) can spend a good amount of time trying to help another person through their issues, but unless they take the initiative to help themselves as well, your time and energy, your support is of very little use. Do what's best for yourself, and in this situation, it will be tough to take the actions you need to take, yet I have confidence in your ability to do what needs to be done.