A psychologist really should have better control of her facial expressions.... but then, maybe it was a reflection of something else, like "that must be really annoying", which is certainly how I find the head-between-the-legs trick!

The good thing about it being your psychologist, is that you can ask! It's a really healthy part of therapy to note how her reactions affect you and your reflection on this is far more welcome than in typical relationships. Do you think you could let her know how her response affected you?