Absolutely not - OP’s gf just sprung a HUGE piece of info that impacts their whole future together. And she spoke about it like it was a foregone conclusion! She does not get to be coy about it now, I don’t care if she was completely wasted. As far as I’m concerned, that’s all the more reason for OP to be worried. People lower their inhibitions when they drink, and they speak the truth. 

What’s wrong with OP saying “hey, I know you were drunk, but what you said really upset me and I’m not comfortable sweeping it under the rug. I’d really like to discuss what you meant, and I can’t feel comfortable in this relationship until we do.”

Your advice to “wait until a romantic evening” is bizarre and that will DEFINITELY ruin the vibe of OP’s nice night.

OP, Address this now. It was an insane thing for her to say and then refuse to talk about. She doesn’t get to pull that shit.