It'd depend on whether the girl in question is of the thawing "classic" type or the oscillating "modern" type, but since Louise is the modern type let's think about that.
The oscillating tsundere is a prickly, explosive ball of emotion; she lashes out at the object of her affection to disavow it, blind to the fact that her paying such focused attention in the first place is an obvious sign of interest. She pulls and pushes, demands affection but bites and scratches whenever she might receive it.
Apply this pattern to a partnered, post-arc tsundere whose cuckquean nature has begun to stir. As you say, she'll reflexively deny it... and that which is reflexively denied must need surface elsewhere, so she'd unconsciously shade everything else with it. Parts of her life would fall into its concealed orbit: She'd flaunt her man, might even smugly brag to her friends that she can barely keep up with him in bed, but would burst into nervous anger should any of them admire him. She'd point out other women to him, supposedly to prove that he doesn't need anyone else but her, and then berate him for looking. She'd accuse him of lusting after her friends in strangely graphic detail, each time a different repressed fantasy, and then jump his bones straight afterwards—just to mark her territory, of course. She has to make sure her man knows who he belongs to, that's all! Baka.
But all tsunderes must eventually snap—the only question is how. Will her man, already wise to her tsuntsun ways, eventually pin her down and rip off her soaked panties when she's in the middle of ranting about how he probably wants to fuck her better-breasted friend in the ass? Order her, through her sudden shocked silence, to keep talking as he slowly slides into her soaked slit? Say, smugly, just before her moan-slurred monologue chokes off into the speechless panting shudder of the hardest orgasm she's felt: "Actually? That sounds kinda hot."
Poor little vulnerable torn-up tsuncuck'd be in tears afterwards—of shame, of defeat, of overwhelmingly happy relief, and of feelings she hasn't names for yet... but soon will.
Or maybe the coincidences would continue to pile up. Maybe she'd start schlicking to thinly-disguised fantasies of him cheating on her, just to make herself feel better, to reassure herself that she was in control. Ah, but she'd never—she's not that kind of—threesomes, perhaps? No! No!
Why should he be allowed
to enjoy himself like that when he's making
her be so upset? The rest follows: Endless internal bargaining, eyes empty, attention distant, outbursts more and more random, everything less controllable, an invisibly thin membrane of rage stretched over the world. If things got really bad, the kind of bad that needs to land someone on an analyst's couch but rarely does, her abusive side would become an outlet. The more she schlicked, safely numb, the more she'd berate him afterwards, the more he'd feel pushed away, the less sex they'd have, the more his needs would compound—and then? Why, he might well cheat, just as she expected him to all along
. All men are bastards; you can't trust them! She'd get what she needed, both things—the desire, as well as the poisonous disavowal that protects her from experiencing it... but not its consequences. Round and round and round and round, a spiral so beautifully distracting that she wouldn't be able to notice the yawning void at the bottom until it swallowed her up.
(Didn't go how you expected? Don't worry, this girl's hypothetical. But she does show us a danger: One must never allow the fantasy of one's man dipping his nib in other inkwells to offset any affection you don't provide him in real life, because then it's not a fetish, but a symptom
Dial back a little, take out the dysfunction. Now the coincidences continue to pile up, but they're happy sexy ones, ones that involve her organizing nights out with her guy and one of her friends (she's so nice!), only for her or be delayed by a completely fake emergency that lets her stalk them from afar—to make sure he's behaving, of course! And when she catches up, the fake emergency having been resolved, she'll give him an earful for being so comfortable with her friend. Just whose boyfriend does he think he is, huh? And they'd smile at her antics, because they know and love her. Wouldn't stop her from crossing her legs real
tight and kicking her foot so that things down below move in just that
right way as she watched them talk to each other over coffee, though. Got to deal with that confusing hot prickly feeling somehow. Fine. Fine! God, these two are just unbearable—fine! They can stop not asking for a threesome so loudly, she can hear just fine, just get it over with. She'll allow it, just this once, but only because they
want it so much, understand? No refusals allowed—this is difficult enough for her already! Now come on, hurry up before she changes her mind, because she's already booked a hotel.
The oscillating tsundere is a prickly, explosive ball of emotion; she lashes out at the object of her affection to disavow it, but she can't run forever—one way or another, she'll get what she needs.