stuff like that happens. The most likely reason is that she probably got a better offer and blew you off. I understand scheduling far ahead of time, but I also think you waited too late to confirm with her. I think you should have contacted her maybe a week in advance of the date. That way, you have some to play with if she does not respond immediately.
Yeah, it sucks that she treated you that way, but it is one of the hazards of the hobby. It happens on both sides of the counter. When it does, you just have to move on. Just because she is considered a top provider is no guarantee that she will come thru for you. Learn from the experience.