This might be a good opportunity to practice confronting someone and standing up for yourself and facing your fears of upsetting someone (if she takes it personally, too bad). Of course she might take it personally-someone is telling her she is doing something disrespectful, which reflects negatively on her. She'd take it personally if she thinks she does no wrong/has trouble seeing her faults and shortcomings since she doesn't have the self-awareness to see this. But a person with an average amount of self reflection would be ok, someone above average would be glad to be told. And a therapist should see how their behaviors affect others. So if she feels reactive, that's on her.

You could keep the option of cancelling appointments as an escape.

But maybe you could turn lemons into lemonade here. Best of luck.