i feel you man. and i know it's easy to say on my part because i'm not in your shoes. but here's the way i see it (and i was actually gonna make a post today about this).
Usually you feel that way because you feel like you didn't come out with your best foot forward. Maybe you feel like she hasn't seen your full potential and that's why you feel like contacting her. You feel like you could contact her and tell her exactly how you feel with the right tone and delivery and she'll give you another chance.
Let me tell you something man. for whatever reason (maybe it has to do with you, maybe it doesn't) she flaked on you. Maybe she felt something wrong on the date, maybe she didn't like the fact you called late on wednesday, maybe she didn't like your shoes, maybe a better option opened up somewhere else. who really knows. my point is, whatever the reason is, chances are you won't be able to convince her otherwise even if you talk to her. She acted like a coward. if you contact her, you are rewarding cowardly behavior with more attention. As soon as i would have heard the "maybe" i would either have either tried to force a solid yes or i would have did like you did (say it's cool) and already mentally categorize it as a likely future flake. the ball is in her court. If you contact first, you taking an option away from her. By contacting her you're depriving her of the option of doing the right thing. Give her the opportunity to learn respect. then it's up to her to either accept your guidance or not.
I won't front, i slip up at times. i'm far from perfect. and sometimes i cheat a little bit and tell myself "i'll teach her later down the line. i'll give her a pass on this one." Problem is that if you do it too much you end up with a very bad student. it's your call but like i said, i think it's at a point where it's in her court.