I use first names only. She does know their relationship to me (sister, friend, colleague). That's all.

ETA: I used to say things like "that one colleague I really hate" and "the colleague who is lazy" but I slipped up a couple of times, figured the cat's out of the bag, and now I just use their names. My T has a good memory for names so it's not an issue.

If I were talking about something reportable, I think I would tell her the basics without names, then ask "is that reportable by you?" and proceed from there. If it's not reportable, I'd go ahead and use names.

I think it's harder for the therapist if they know the names, especially if it's a unique first name, because what if they know that person in some other context? But that's not my problem. I don't worry about it.

A colleague referred me to this T and had seen her before. Maybe that colleague talked about me, or about the same people as I do. (We have the same boss.) I don't know and it doesn't bother me because my T is so good at being there, for me and no one else, during my sessions.