Explanation

How shall I put this?
When you have a boyfriend, generally you go to prom with said boyfriend.
When said boyfriend splits off of his original prom group, generally you go with him. After all, he is your date. It's awkward for EVERYONE if you don't. So GO WITH HIM!!! If you don't like the group he's going with, convince him to switch back, but don't NOT go with him because you don't like his group. I mean, if he's your DATE you should spend time with him, yes?
Yes?
Is this a hard concept?