Do what you need to do to get your daughter out of there, and by that I mean drive and get her. Don't let your ex know you are coming, and be careful about how you communicate that you are doing this to your daughter, just to help make sure that your ex doesn't find out.

Once you get her home contact child services in YOUR state, you are going to be in for a bit of a fight, but if you are going to fight, do it in your home state, with your daughter in your custody. Let your ex take you to court, let your daughter tell her story to the proper authorities.