She can't understand why he hasn't confronted her about her suspicions, now that they've been proven untrue.
Could it be that there was something to it after all? No, impossible. But maybe there's something else, something he's not telling her, something he feels guilty about. Maybe that's why he hasn't picked a fight.
Or maybe he doesn't care about the way she acted. Maybe all the time she was upset he didn't even notice. Or maybe that's what he expects of her, maybe he sees her that way - as shrewish and untrusting.
Or maybe it's all a ploy. Maybe he's saving it up for the future, planning to use it against her the next time they have a fight. Maybe he thinks he can punish her more this way - by pretending to be the bigger person.
Or maybe, just maybe, he actually is the bigger person?
No, she doesn't think so.