I have been thinking about this and I don't think I would friend them.
I suppose it's the same reason I didn't want my therapist to do any self-disclosure at all - I want the relationship to remain something that exists only in that room. I've softened my stance on the self-disclosure, but if I were to run into it on fb, it would be different and I would feel different about it. Right now self-disclosure feels like something she's offering to me in the intimacy of the relationship. To see it up on a public billboard would not feel so great to me.