Well, I have been throught something very similar to this with my daughter and her stepmother and father. My daughter lived with them from the time she was 6 years old and we had joint custody, however, they lived in San Antonio and I lived in Dallas. They did everything in their power to keep my daughter from me and told her terrible things about me. They tape recorded our phone conversations (if they let me talk to her at all), didn't allow me to come to her extra-cirricular activities, didn't tell me anything that was going on, but wanted me to pay my half of everything! Anyway, long story short, there wasn't much I could do but continue to put her best interests first, never bad mouth them to her, and try to make the best of the situation. She is 20 years old now and we have an incredible relationship! She has come to realize the things her father and stepmother did over the years and she is very resentful about it. I know this advice is probably not what you wanted to hear for the short term, but unfortunately, you can't be reasonable with unreasonable people. You just have to have faith that you are doing everything in your child's best interest and you are staying in the child's life regardless of the obstacles she places in front of you. In the end, your relationship with your child will blossom and hers will deteriorate. Hope this helps.
K.