[Doesn't jump, obviously, but tenses up - taken by surprise that someone would have approached him while he was distracted with thinking]
[Turns around to face her with a frown - at this point used to people knowing his name, but it's clear that he doesn't recognize her at all... aside from the slightest hesitation, because, well, out of everyone here she seems the most like someone he'd know - her state of dress, and the fact that she looks like a younger version of his mother, maybe.]