I agree with Willybluedog -- that there are red flags with this kid that should not be ignored. I would try my best to educate her about abusive personalities/relationships so that she might be able to recognize it for what it is. There are good websites dedicated to educating young people about "teen dating violence". When a calm opportunity arises, maybe you can direct her to the quizzes at
www.loveisrespect.org. Maybe it will help her to come to her own good conclusions. Beyond that, keeping your own boundaries firm is definitely a strong message that something is not right here!
Another website is
Love Is Not Abuse - Home
Good luck!!!