I think it's business courtesy that you let your T know if you're not going to be showing up. Otherwise, she would be waiting there for an hour without a clue what was going on. And possibly worrying, if it's not like you. I don't think you owe her a lengthy explanation.

The not chasing part would be her holding back from trying to convince you to come in despite you trying to cancel. Like any other professional, if you have an appointment and don't show up, they will call to find out what's going on. My dentist, hair stylist, mechanic, etc would do the same.