I've bumped into my T on many occasions and she will smile or wave or talk to my 5yr old if he's with me but that's about it. And that's only if I'm comfortable with it. There are other times we have seen each other and haven't acknowledged one another when she has been in the company of other people. In session we did talk about this and she doesn't like to chat outside the office publicly for privacy reasons other than a friendly hello, wave or smile. She leaves it up to the client to initiate a hello for their own privacy.