Oh, that sounds hard and unnecessary (and I have a music degree too!). I totally understand why it was triggering for you. It sound unresponsible of your school to allow this class to happen when it is being led solely by someone with no psych qualifications.

Definitely talk about it with your T. Is there any way she could write to your Dean of Music, saying she is treating you and that taking the class would be detrimental to you mental health? I was in a bad way and seeing a T in my last year of Uni and she wrote to my department asking for extra time for me to complete certain assignments. It wasn't a problem. Your T shouldn't have to give any detail.