My T did explain that there would be a charge if I didn't inform her before 24 hours to cancel a session, but if I had to cancel and change the date or time it was always well in advance.

I'm unsure if she is strict with the charge, but I think it's fair to charge if notice was not given. She could have filled that spot for some other client, and she is in private practice. I know people who are so irresponsible and neglect to check their appointment times or are always late or no-shows. One of my pet peeves.