Hi there, and welcome to the dissociation forum.
Like you my long term ex-T didn't initially know anything about DID. (I had brought the diagnosis with me from my previous T in another city). She was willing to learn though, and consulted with others and joined ISST-D etc.
The guidelines my ex t worked with are that she would actively communicate with whoever presented in therapy but not call them out or address them by name. she did acknowledge them though... like if she noticed 'x' had come out she would say 'hi' but not 'hi x". She didn't ignore them. but she would never say "can I speak to ....?" except for a couple of times when we asked her to if we got stuck when working through some harder stuff.
it sounds like an oxymoron I guess but she treated us as one while at the same time acknowledging (perhaps more subtly than directly) our differences.