I'm going to refuse to go to prom with my gf
That doesn't sound very nice. Do you have a good reason to miss your gf's prom?
I want to go to a party with my friends instead. A prom feels like a torture chamber to me. I don't need my girlfriend to threaten me with a prom.
You can always party later. Prom only happen once.
Don't tell me what to do.
If it's really important to her you should go. That's what good partners do, they do things that their partner wants from time to time.