I want to ask this girl to a school dance and then hook up with her at the after party, but she doesn't drink. Should I still try to go through with this? Could I still drink, or is it best if I don't because it could make her uncomfortable.
Don't plan sex.
Don't plan the evening.
Just ask her off the cuff if she wants to go to it, like its no big deal.
If she says no, its fine.
See where the night takes you.
Drink if you feel like drinking.
tl;dr Do what you want to do.