I've had two or three dreams about my therapist during the past year, mostly calming too. It makes sense to me they'd enter our subconscious as a symbol of comfort given the supportive nature of the relationship. However, my own therapist would note that our dreams typically represent aspects of ourselves and help us process our waking life as well as show us where we are in different, symbolic ways. She talks about houses as representative of our lives, and people as parts of ourselves.

Anyhow, sounds like a nice dream, even if you were a bit surprised by it.