I'd probably feel the same. Grateful for the call on a holiday, sad that she said she might not remember to call. It would have been kinder for her to leave that detail out and just asked you to initiate the call. I think it is fine to feel both at the same time. I probably wouldn't frame it as a complaint, but in a fact giving and curious way with T. "Hey, I feel grateful for the holiday phone session, but I also feel hurt that you said you wouldn't remember to call".

I do think that if T offered a session on a holiday, it's her choice. Unless you were somehow begging or manipulating to make that happen, she is capable of making that decision based on her schedule for the day.