Is there someone higher up in charge? - I would want to mention it to the director or supervisor as that is not a good reply IMO. I wouldn't worry about not addressing the girl too much, perhaps discussing B's reactions/feelings about it would be more beneficial and useful. We have had some discussion as DD1 had issues re punching and kids not wanting to 'be friends' - at 3!!! So I have just been trying to build up her confdence to walk away and not pay too much attention to these kids - trying to give her an internal dialogue that is positive rather than negative. Good luck!!!