There is something you know though, you've done it once before and that shows how resilient you are already. You can and you will get through this too. I don't know much about DID, but maybe also working on this alter feeling safe and grounded first would help before unpicking more trauma. If you think you need to go though it at a slower pace, tell your T that. I think it's also helpful to have much lighter sessions as well, even if you don't talk it's all good. There was another poster whose T would read books because that's what they needed.