Awww, I'm so sorry, BlueMoon!
Yeah, the timing of this all sucks, but at least you were able to get that appointment in with your daughter's principal. And then, like Tree said, this allowed time for your current T to call. I swear, the way she talks to you - I don't like it!

I understand and respect that T's have schedules for a reason, but it's also a business where changes happen all the time in scheduling. My T asks that I let her know a week in advance if I need to reschedule, but I've called her 4 days in advance, and she was so supportive and told me not to worry about it at all - that's how a T should react! What is your current T's cancellation policy? If your current T has other patients who want those slots, and you continue to cancel them week after week, I agree that it's best to tell her by next week that you want to take a break. But she should at least hold those for you for next week, it's different if you did this every week - but this is the first week you've canceled like this, right?
Definitely give this T another try. But who knows, maybe you will interview the next T on your list and click with her, and then you won't even have to reschedule with the flat-tire T.
Don't give up! And be good to yourself today, you are worth it!