First off, dissociating is not only a symptom of MPD (DID), I have BPD and I have Dissociation.

Also there has been a huge controversy over whether or not MPD actually exists, it has been found that in the majority of cases it was found that Therapists coach the client into it. I wouldn't be surprised if your T was trying that (Of course she would be nice) but I of course have no idea.

I agree with the others, talk to her!