Part of it is ... how small is their society?

I mean, if you're going to keep running into someone party after party - and this *is* a very small closed society right now - it's probably easier to be friendlyish.

It seems, like from the various interactions, it's not so much a "Our respective adults are friends, so, yes, we should be" but "Our paths didn't really cross directly at school, but if we're going to be at all the same parties, might as well get to know each other a bit better."