Hey guys. Original OP here. Sorry for reviving this old topic, but I never got a chance to reply, and feel I should.

Thanks a lot for the advice everyone!

I feel I should clarify—I had known the girl as an acquaintance for a while, and there was always chemistry, but nothing had happened up to that point. Yes, her attempting to make me jealous might have been in my head that night. But I have definitely had it happen with girls on other nights- now I think about it, always girls who I'd known them for some time, but who I was not yet in a relationship with. And I agree with what people have said: I haven't had this situation happen with girls I've just met.

From reading the replies (esp. Joker), I get the feeling that the best course of action is to just go "fuck her", and go off and chat to some other girls. Not from a weak stance—where I'm not getting engaged in the new conversations, and consistently looking over my shoulder to gauge her reaction—but change my inner frame to genuinely forget about her for half an hour or so and have some fun.