That would solve this problem, but still leave Granite open to being triggered again somewhere else - in a place and time when T is not there to help.

There is an opportunity here to explore with T what "being put in the corner" does to Granite, and I think she should use that if she can.

FANTASY DIALOG:

Granite: Last week I was triggered when I found the chair in the wrong place and it wrecked the whole session. I thought you had put me in the corner deliberately. I felt (insert your feelings here).
T: I'm sorry. It was an accident. But let's talk about it.