Why should you have "faith" in this therapist? Either there was a miscommunication or she didn't trust you would follow through AND felt justified in going behind your back. Even if she didn't technically violate confidentiality in an illegal way, what she did is shady. I'm not really sure how there could have been a miscommunication, as it seems unnecessary for her to have told your psychiatrist if she heard you say you were going to. Maybe she thought you would forget, and it wasn't about not trusting you per se, but infantilizing and micro-managing you. I guess that's possible, but it would be overstepping for her to do that. You guys made a plan and she should have respected that. In fact, I don't think she should have spoken to him at all if you told her not to, regardless of agency agreement. You have the right to revoke your consent at any time. That may mean you can't obtain treatment from multiple providers at certain places, but you always have the right to withdraw consent.

You're definitely not going to hear any reasons from me that you should try to "have faith" in your therapist.