Should I go to the after party or not?!?

It's my school's prom on friday and my friend was supposed to be having an after party but she's decided against it at the last minute. Another girl in my year is having one but she's a total chav and I don't really want to go. It's �10 to get in and I think that seems alot seeing as I don't want to go and I just don't think it would be fun! I know I'd be way to uncomfortable to drink in front of all the people from school as I know they'd all be judging me and the dress I got is quite low cut and short, when it was amongst friends it didnt seem to bad but I know I'll feel over exposed and self concious. I'm not exactly high in the school hierarchy and for a while I was under the impression I wasn't even invited so I don't really want to to go to a party with people who don't want me there and will probably be taking the piss out of me and laughing at me. But then on the other hand I'm worried it won't be as bad as I'm thinking it will be and I would have a decent time, all my friends are going and I don't want the rest of my year to think I'm some pussy who doesn't want to get pissed! Because I do! I'd just rather do it in a place I feel comfortable, with my friends and feeling confident! My friends think I'm being silly and maybe I am but I feel like none of them really understand where I'm coming from and I need an outsider opinion. Thanks for any thoughts.