making fun of

I'm in a group chat with some people I will be attending college with next year and I'm only in it because this guy I'm sort of dating is in it and it's all hide friends really, I don't really like them so I don't consider them my friends. There's this girl who's going and she's obsessed with my boy. And yeah it annoys me but I'm not that insecure to really care. It's so obvious to everyone though. And all these kids do is make fun of her behind her back in this group chat(she's not in it) and I know she doesn't know but it really shows all of their character. And I know people don't realize a lot of the time when they're being this way since they just assume she won't know anyways. I wanna text my boy and tell him that it bothers me but I just don't know how it will affect our relationship, he's nice and sweet to me but honestly an ass to everyone else(which is probably why I like him🙄) but I'm not like that. I don't make fun of people for entertainment because I just find it mean, so how do I tell him that because it's important to me and if he can't make a change to not vocally speak those unnecessary remarks then I don't want to be with him.(but I really do want to because  aside from that we do get each other)