We can pretty safely assume OP is also drunk
How? Pre-gaming doesn’t typically result in being drunk, it’s something you do to cut the costs of getting drunk at a bar. It’s usually something like 1-2 drinks, so you’d be a little buzzed, but not drunk. If he was drunk, I highly doubt he’d have the fortitude to refuse, because alcohol dramatically lowers your inhibitions. It could also be that OP doesn’t drink, he just went because he likes the girl.
So no, I don’t think we can safely assume OP is drunk. Also, you don’t throw up alcohol until after you’re already drunk, so throwing up most of the alcohol isn’t going to sober her up.
It can, but I’ve “pre-gamed” with people who are drinking without drinking myself. Designated drivers are certainly present if the bars aren’t within walking distance. Generally speaking, people don’t get drunk before going to the bar, because the bar won’t let you order if you’re visibly drunk, and why would they allow you to stay if you’re not a paying customer?