C.M.
I've been in this exact situation before. I did, ultimately, make all play dates at my house so that I could have more control over what happened. We didn't have a biting issue, but there was occasional kicking, lots of screaming and tantrums, and definitely a lot of dangerous jumping on furniture issues. I just held the line that we didn't do those things here, that he could do those things at home by himself if he wanted. I also used the opportunity to try and drill into my daughter about how it's ok not to ride along with everything that's happening around her. She was only 3 at the time, but really seemed to understand it when we discussed it. I did occasionally "catch" her, at my friends house, doing what he did, but she also was aware that she was caught and was really only acting in a way she had been told she could act by the other parent. (This is when I started insisting we play at my house). I will say that in the long run, my friend's parenting style caused us to drift apart. But I will also say, that her son was eventually diagnosed as ADHD and that I regretted not making a bigger effort to support her, or encourage her (more than I did) with him. They still play together and I try to love him unconditionally, because I think every child needs that, but I do watch the play carefully and remind him of his influences on my younger children (the kids are 9 now). I think with divorce in the picture, that surely has an influence on his behavior. Perhaps you could even gift her with a book on children's behavior during a divorce. Good luck!