HELP MY BF AND THIS GIRL

so basically we have never had girl problems or anything like that . Until this year that this girl started being a stalker she will always come up to my bf and try to talk to him and at first he was like mmm wtf and then they became “friends” but I rlly didn’t care much Bc he can have girl friends but I cared when she started being flirty. This girl flirts with him all the time and she makes up anything just to talk to him and he goes along. My bf is a rlly slow guy but that doesn’t excuse him form anything. He says she doesn’t do anything wrong and that I’m jealous and controlling when I have never told him to not talk to girls or anything like that. Everyone tells me how they notice and I see it to so I told him I don’t feel comfortable with him talking to her and if he can be dry and he said he will be Dry. But he isn’t like she talks to him all the time and I can’t do anything Bc is during a class and I hold a important position so if I do something I could be removed from it. Anyway, This girl has a record for being obsessed with guys but no one likes her. Like no one does. And she keeps being like that and my bf says she doesn’t do anything wrong and he doesn’t care about my feelings. He defends her . What do I do? Am I being jealous? Like I have no idea what to do help