If she doesn't want to go, she won't. The best thing you can do then is give her support and hope it doesn't go too far. She needs to realise that this person is not doing it because he loves her, but because he likes the power of controling someone.
If she wants to leave, she just has to leave. Not let him spreak, just grab her bags and go!!
The turning around thing will only work if she really wants to stay and put efford in this guy.
I have been in a relationship like this, I hope that things will work out for her. It is very though to break out of a relationship like this.