I'm coming in a bit late on this thread.... but I definitely would not allow this T to share any further information with your parents. She is correct in her assessment of her own inabilities to take you any further in your therapy. I agree with you that she may hinder you if therapy proceeds "as normal."

However, yes, she can assist you with basic support in coping during this time of change for you. Whether she believes in DID or not, or is just still coming to a decision about it (maybe she has to answer to someone who insists DID never be accepted?) doesn't matter when it comes to the support she is to give as a therapist!

Maybe really good therapists are still on the fence about this disorder, and unless they irritate the patient, like your T has, they can generally help the patient to healing. It isn't supposed to be about the T, it's all about the patient! Your T seems to have found her limit and is showing her frustration in not being sure what is best for you? IDK.

Yes, seek out a new T in the other area, one that is expert in PTSD AND DID. (There are those who are DID without suffering PTSD ... )

This T has lost your trust, and you owe her nothing. I doubt you should share anything further with her, unless all of you feel safe doing so. But again, I would definitely put it into writing and sign it that she is not to share any such information with your parents, just so she's sure.