Sounds to me like the misunderstanding hit a nerve that you personally have hit many times before. When whatever-it-was-that-happened happened, it brought up a whole stream of other you-centred unpleasant memories/feelings/sensations, such that she went through it all again. So when this one was cleared up, there was still all the other gunk that's now floating through her head, even though it's not relevant this specific time. Plus it also reminded her how the relationship isn't perfect (basing this off Ni creepiness) and maybe she wants you to be more loving and smoochy or whatever, I don't know.
She could just be in a bad mood.
And maybe when she felt distanced because of hurt, you didn't cross the gap to bring her back with love and reassurance and whatnot. Basically the 'emotions linger' thing. Except it's not so much the original emotions lingering as the fact that not reassuring her after she's hurt could lead to her feeling hurt all over again.
If you sort of smother her for a bit, in whatever way's suitable, it'll all probably go away.
I don't know your fiance though. This is just based on general stuff I've observed. Anyway, if she has a tendency to be wounded, she's going to keep being wounded, over and over again, if you don't patch her up. Especially in stressful times. (Add the disclaimer again.)
Could be your tone of voice too. Maybe you sound rude/uncaring/cold. Content would be irrelevant, hence the hurt remaining even after the misunderstanding has cleared.