Look for a different partner. If he goes to the prom with you, he'll most likely get problems with his girlfriend. What you could do in my opinion is ask him whether he'd like to go with you while telling him that you know he has a gf and you only want him to go with you if she's ok with it.
maybe she likes another guy? idk that is really stupid if she doesnt want to go to prom with her own boyfriend, ask her whats up
Question yourself whether you should still want to go to the prom with this girl.
dude, chill. although you really don't want to take her to prom, you already said you would. do not let her down. or if you want to hurt her feelings, either break up with her or come up with an excuse such as my mom is sick or i'm going to visit my grandparents.
go have a root
get over it
Just say, "I'm sorry, but I don't want to go to the prom with you"
Do not go with them if you don't want to. It's your prom, so you should enjoy it, not be miserable.
You don't... if you love her. Just ask her, if she doesn't want to, find another girlfriend because she is not truly bisexual in that case.
You respect their relationship. If you were in the girlfriend's place, how would you want another girl to behave?
Because he is a man
nothing if you can't trust her you don't want her!
Because they want to show you that they are happy with you going with them to the prom.