My daughter resides in Maine and I live in New Hampshire

My daughter resides in Maine and I live in New Hampshire. My ex has told me that I can no longer see my daughter due to a dispute as to who will have for the holiday. The agreement was that she could file taxes this year using the deduction and I would have my daughter for the Christmas holiday. She is now telling me that I cannot have her and she is going to use the tax deduction anyway. She has used my daughter as a bargaining chip in the past as well. My question: I need to take her to court to try to stop this from happening year after year. Do I have to file for a court in NH or ME to be heard on this?