I need help with high school relationship?

There's this girl I really like, and I've had a crush on her since last year. I don't know her personally but I do know her personality. And my original perception was that she was a great person and that she has a really "sunshiny" positive attitude. So fast forwarding now to this Thursday I think. One of her good friends is in my math class and I was talking (purposely so she'd over hear) that I was having a party over the summer for my birthday. Then she was like "Oh i'm not invited". Well interested in the potential prospect I said "oh no sure you should go" and I must've done this very excitedly because she referenced it later. So as I'm walking out of class my friend made a comment something that implied I was way too happy about her going and she was just being a ***** and joking. So I here at lunch from my good friend who was sort of in the conversation, that the girl in my math class was talking to my crush, and imitating me in a really gay voice saying, "Oh you should def go". He told me and I've been really upset about it since, especially since I've had such a crush on this girl for such a long time. And apparently they're going to show up like really drunk and just sort of screw around. So now I'm wondering, do I tell her how I feel when she's drunk. Should I tell the girl in math class "I know what you said, you're a *****.” Please help me because I’m really upset and unhappy and don’t know what to do. Also if I ask her out, then she might tell everyone in the school and embarrass the hell out of me. I mean I’m a nice guy but shy and quiet, and I’m a loser in highschool and I don’t get why I’m seen as unappealing. I’m smart, handsome, athletic, and friendly, but I’m still looked down on.