It sounds like she believe she knows you better than anyone and she has decided you don't have dissociation. Or she has decided you don't have it because it doesn't exist. It would make me feel hurt as well. Especially if it was wrapped up in cowardly behavior.

This is very far fetched but maybe she has a phobia of her maybe having dissociation too? Maybe she is fearful.

I hope you guys can talk this out and still be good friends. Sometimes friendship is hard. The other day when I had a bit of a stress related breakdown my friend wouldn't comfort me at first because she didn't accept the stressor. She said it doesn't stress people. Well it stressed me into severe fatigue. It does hurt when you're not heard or understood.