Hmmm - wee sh!te. if it's anything like what happened in my case, i'd expect frost relations with next door. When my son was bullied at school, we went straight to the school - there were a group of boys involved with 2 main ringleaders and I knew one of the boys parent quite well socially, I went to the school because I suspected it would get into a he said/she said thing. However, when the school called in the parents and they found out who the boys had been bullying, the parents came round to my house and apologised and got the boy too as well. When I was in the playground the nxt day, more of the parents were so apologetic and upset about what had happened and the all said that if anything should happen in the future, please to let them know. Couple of months later I personally witnessed an incident and told them, they didn't want to know, felt I was making it up and they implied that it was my sons fault for being bullied! Safe to say that the next time I went straight to the school and let them deal with it. We don't speak at all anymore. It's not so much that their son is a bully that annoys me, it's the fact that they know he is but are doing nothing to stop it.
I sincerely hope the school deal with it, and I also hope that his mother sorts him out, but i'd be prepared for her denying it and saying that your daughter is making it up.