I have someone in my life very close to me who is diagnosed with DID. They see one of the best therapists in Ontario who specializes in trauma therapy and DID.

I would never "play therapist" with them because it can be super dangerous to have someone with no experience or education try to do so. You could unintentionally cause further damage even if you mean well. Aside from that, I think it would come across as insulting and belittling, as someone above mentioned. Leave this kind of work to the professionals.