She's happy to be corrected in this case, viewing it as a chance to learn a little more. (And entertain herself). The interest on her face is genuine- well, naturally. If she weren't interested, in this case she probably wouldn't pretend. She knows the value of feigning fascination when it might further her own causes, but right now there really wouldn't be a point.

"I see," she says thoughtfully- and then, because she can't go for too long without pushing and prodding people to see how they react, adds with a kind of sharp smile, "and are you good at your job?"

It's not a terribly normal question, but the smile suggests she knows that. Anyway, she's not a terribly normal person.