Would you be uncomfortable if your boyfriend went to prom with someone else?

My boyfriend and I are in college, but he just informed me that his friend who's still in high school asked him to prom(really short notice). I've met her and she seems nice. But he has told me multiple stories about her being really promiscuous... He thinks prom isn't a big deal, but I kinda do. There will be dancing, and knowing her, it will probably be really dirty dancing... I guess what bothers is that he didn't even ask me if I cared or not, he just kinda told me. I didn't tell him it bothered me, I simply said "It's up to you" and he responded with, "I know". He hasn't decided yet though. Would this bother you?