Aww, adorbs
I think from what I know about Lily and from the look of the situation as it is there -- maybe a little of column a, and a little of column b. No way would she agree to become intoxicated with a dude unless something pretty significant happened before that.
I imagine sometime early in their acquaintance-ship, Lily said somethin' expecting a "Not all men" comeback, except Bruce probably agreed even more fervently that all men suck, or something, which took her aback, and she decided to re-evaluate this one. So like, they kept talking. And incidentally in the meantime she's becoming more comfortable with socializing with dudes b/c of Jamie's presence with Ellen. Eventually Lily realizes that she is, unexpectedly, completely at ease with Bruce.
I donno if they've hooked up in a more 'romantic' way, beyond just hanging out and engaging in the depicted activity. I donno if it matters. They look happy with each other, regardless, and I'm happy to see Lily happy about
anything