Lily,
Hi and welcome to PC!
I'd be very surprised if your T didn't know when you were dissociating even if you didn't mention it...they all seem to have that spidey sense that let's them know when something's up.
But regardless...can we analyze your fear? Is it the fear of the words or fear of letting someone into your private world? Obviously you were triggered and distressed by something that happened in T, or you wouldn't be dissociating. So I could completely understand why you wouldn't want to let T know that you were checking out. But I can also relate to not wanting to put words to it at the time it was happening...for me, it's a control issue. Tho I've been dissociating so long it almost occurs without conscious knowledge, on the occasions when I know what's going on, I'm usually angry with the person for "making me feel that way" (yes, I know that no one can make me feel a certain way, only I can do that) and so the last thing I want to do is tell them I feel vulnerable.
OK, wow. Sorry. I've made this all about me.
Maybe you and T can work out a signal or code word? If you said "purple monkeys" for example, she'd know you were getting distressed and could help ground you.
Keep posting and again, welcome!
Bub