It sounds almost like you were going into physical shock because of how strongly that voice affects you... but your T is there to guide you out of it. And I like what lolagrace said, you'll be able to internalize that calming down process eventually... you'll hear your T in your head instead, helping you calm down. That makes me wonder... would your T let you record her, talking you through some of the relaxation stuff? If you could listen to her voice every day and practice that, maybe her voice would grow and counteract some of the other internal voices, a bit.

I've only been terrified once in a therapy session and it was a bit different (felt like I was sprinting, I was out of breath and thought I would have a heart attack)... but unfortunately I think that's how we know we're getting to something very important. Really brave of you granite.