"I need to look at one of those books for a few minutes," she says, not evidently put off by the brusque tone. "You can have it back when I'm done, but I've got someone waiting on this report and I don't think she'll accept 'I took the rule about no talking in the library too seriously' as an excuse, so."

She's neither offended, nor placating; in fact, her demeanor suggests that they are both reasonable people and, as she's making a reasonable request, there's no reason he should make any particular fuss.