K.T.
although my children are younger, I found a great book on communication that is easy to read and very revealing. It starts with 'how to talk so kids will listen so kids will talk and how to talk so kids will listen.' then it's 'how to talk so teens will listen and how to listen so teens will talk.' it's at any bookstore for like $12. Don't let the simplicity of it's writing make you think it's not valid, it is very valuable for communication.
I just went through a nasty divorce and my ex-husband is always scheming against me. He puts the kids in the middle and tries mind games. What that taught me is that I cannot control the situation. I can only do my best, and realize the kids will know the truth, eventually. If they get mad at me, I can't do anything about it. I'm not giving up, I am just being the best mom I can, despite my situation. How this relates to you is that if she does go to live with her dad, and you have done everything you believe you can do with an honest heart, let her go. Keep loving her, and tell her that you are there for her. When she is ready and has had some distance, she will come back to you. At her age, it may be something she needs to work out on her own.
Take care.