"but not because I think she did anything wrong.. just that I feel my reaction was inappropriate"

Why does it have to be you? That's what I wish you'd discuss with your T; it could in fact be her. We can't assume she was sick (we can but that's an assumption and basing our lives on unchecked assumptions is not a great idea) she could be out at a really good after-Thanksgiving sale with her mother!

But back to the question of right/wrong and appropriate/inappropriate -- they're the same thing and none of those words should apply! No she's not "wrong" but your reaction is your reaction and can't be inappropriate because it just is. Your thoughts and feelings are as valid as anyone else's. I don't think her cancelling is wrong; if she wasn't in fact last minute sick, I think her timing was crummy.