It catches her off guard, a little, which is no doubt what he intended. So her showing up hadn't been a complete surprise-- unless he'd thought, or hoped, that she'd try to turn it down. (As if she could; she hardly has the standing to refuse an assignment.)

"Constant questioning is a fundamental facet of science; there's no understanding that can't be used as a stepping-stone to learn more." It had been... bold. She recognizes that, but what's wrong with boldness? "Have you read it?" she asks, deadpan but halfway joking, because why would he?