How old is the girl and her psycho boyfriend? Maybe you should write an annonymous (unless you want to say who you are) letter to her parents from a concerned friend and give them a heads up on her situation, especially if she is under 18. I don't think there is much you can do other than to try to give her advice and be there for her if she needs to get away from her boyfriend/ needs a safe place to stay. She has to make the decision to leave, and when she does, she has to make it final. If he threatens to harm himself or another person, she NEEDS to call the police and should definetly get a restraining order against this guy. There are things that can be done, but not much if she isn't willing to stand up for herself. I wish her the best and hope she leaves him before he gets really physically abusive. She's lucky she has a friend who cares so much.