So i'm supposed to be seeing a girl this weekend. We lost our virginity to each other years ago, she's already confessed (while drunk) to still fantasizing about me, and on a purely physical level, i know she wants it. She does have a boyfriend however, and she's resisted even seeing me previously because of that. But she has agreed provisionally to seeing me this weekend, so....i don't know. I'm pretty sure she'll flake.

How do you deal with a flake in an adult, non bitchy, idgaf way?