I have seen this dilemma from both sides-ds went through a stage of biting before he was able to talk. I had to be inches away from him, help him to communicate what he needed/wanted, make sure I helped when another child was taking toys, being actually unkind to him so that it rarely got to the point of swooping in and moving him as he went to bite, and only very, very rarely got to the point where he actually bit. In that circumstance I would remove him from the play, apologise both to the parent and child and get him to do the same, and when (as happened in the most part) the parent said "don't worry, it happens" I would say "that's very nice of you to say that but I know how hard it is to see your child hurt and I'm sorry it got that far." I also, fwiw, empathised with ds because often the child he wanted to hurt was interrupting his play in some way and I never saw him bite/go to bite in order to take someone else's toy. But I knew that, rightly, biting or hurting trumps all other misbehaviour and wanted him to have friends to play with and, selfishly, I didn't want my friends to stop seeing us. He grew out if it as his language caught up.
The other side for us is a very dear friend of mine whose children have hurt mine so many times that I limited how much we see them. Not because of the hurting per se as i absolutely believe its a stage young children often go through however great the parenting but because she believes so strongly in seeing why her child has hurt someone else that what happens after an incident is a talking out loud eg "ah, x, you really wanted that toy, didn't you? And mole's dc had it? That's why you hit her?" Theres no resl consequence, apology or sympathy for my dc, whose only "crime" was to be playing with whatever x wanted. Which I understand, kind of, but is very confusing and unfair to my dc who end up thinking that they were in the wrong. Only very recently has she started removing dc from the play and apologising on x's behalf, saying "hitting is wrong" or similar.
In summary, (!) I feel your pain, the other parent should do more than she's doing and if you feel your dc aren't getting much out of the playtime, then don't see them for a while.