Should I stay or should I give up?

My guy has an 8 year old daughter and a crazy ex-wife. Bn dating for about 4 mos and are really committed to each other n our relationship. The ex hates that he's seeing someone but we talk about it and don't let it affect us. She began using their daughter to get to him. Around Thanksgiving his daughter began making comments about him having a girlfriend and that she didn't want me in their house - she's 8!! So we decided to wait for me to meet her until she was comfortable. I was never in the house when she was -even if she was sleeping. It def put a hold on how much time we were able to spend together and was hard, but we got through it. Then I met her right before the holidays and it went wonderfully! We looked at it as a breakthrough in our relationship and a step toward the next level. Now the ex is putting all of these things into the poor daughter's head again which is basically making her hate me and not want me around her or her Dad (my bf)! We've basically bn dealing with this for the last 2 months. I feel so bad for my bf because I know this is so hard on him. I'm just not sure what to do. Is it going to get better? Should I realize now that it's not and just bow out?