Something like realization sweeps over her face. She'd thought it strange at first, but was her intuition really that close to the mark?

"Well, in that case," she says reasonably, "he must have been offended at you flaunting that you have a lover over him, right? Is it-- Do you think it's at all possible he's jealous?"

Of what, she isn't as sure of, but even if it's not the jealousy of a third wheel, it could easily be the jealousy of someone who has not towards someone who has. Though it's hard to imagine someone so easygoing slipping into a nasty emotion like jealousy so easily...