Bullying by NCP's live-in girlfriends child

My ex and I divorced 5 years ago. I have sole custody of our 8 year old daughter with her father seeing her every other weekend and 4 weeks out of the year. My ex-husband has moved in with his girl-friend, whom my daughter likes and has no problem with. The issue is that her 10 year old daughter has been bullying my daughter during her visitation with her father. My daughter tells me that she takes her stuff, treats her like a slave and has threatened her with physical violence on more than one occassion. She has spoken with her father about what happens, I have spoken with her father about it and he says that he repeatedly assures me that he will take care of it. Now my daughter has come home from another visitation visibly upset, saying that it is continuing and that her father won’t do anything about it. She wants to spend time with him and I want her to also, but I don’t know what to do to stop this from happening to her. She is the type of child that will just take it to prevent her father from getting upset. He lives in South Carolina now… I just don’t know what I can do to help her…I’m struggling with sending her there knowing that she is having to go through this…any suggestions?

You may have a reason to seek a modofication of the current custody order. I would impress upon him that he needs to handle the situation, and if not, have the court intervene.