Hi teachers. Is this OK and idiomatic?

Hi teachers. Is this OK and idiomatic? Is "it all caught me a bit off guard" natural in the context?

A woman came to see me today. She’s been coming for a few weeks. So we were talking... and about halfway through the session I asked her a question that I thought was pretty harmless... but apparently it triggered something in her, ’cause she suddenly broke down crying. And a moment later she got up and left. It all caught me a bit off guard, so I just let her go without saying anything.