my prom date is a dude.

I was asking this girl, I'd like her to be my prom date. She said "sorry but I have a church camp to go". It's fine then I have backups. And I didn't really wanna go with my 2nd choice. So I went to the 3rd choice which I asked her 2 weeks ago that she said "okay I'll go with you". And what she's telling me now is "OMG! I thought you were joking when you asked" . . . . . . Okay so now what? It's seems that I gtg prom with my bestfriend, a dude. FML