Hi Yearning
I've been there. Leaving a T is hard, even if you feel they might not be a good fit anymore. Maybe you feel frustrated but you are still fond of her and look for positive signs from your T? I hate attachment :/

It's not wrong to see other Ts and it doesn't mean you have decided yet. Plus you wanted to talk about it but the session was cancelled: maybe try to see it as more time to think what/who is better for you without feeling pressured. Do you think you can tell your T how you feel and the reasons why you are looking for other Ts but you would be happy to stay with her if she gave you a sign that she wants to work with you? I don't know her so I can't tell, but we are all different and maybe she just didn't realize how much you are actually struggling.

I'd say, feel free to take notes. Just explain your reasons and your fear exactly how you wrote it here, it's crystal clear and shows you are very mature, a good T can only take it positively in my opinion.