Keeping the lines of communication open are most important here... if you can't do that between you and her, then I suggest a third party to mediate.. anyone from a T to her school counselor or principal...

Don't let her go. If nothing else, she needs to know you care enough. Even if she rebels against it, tell her it is because you do care and you are doing the best you can to protect her. When she is old she won't be in therapy because you didn't care enough to try.