Uro and copro = rules. And the rules... well I don't know remember their effect, but probably the slave skill has an incidence on it? Like maybe your mood gets better if she's a good "toilet"? I'm not sure actually, it should be investigated.
And I think during Active sex there are some fetish options you can use.
Enema = there are certain NPC that require good enema skill.
But your ideas, they are interesting, but no, they are not in the game.
It's true that fetish skills have little use in the game. I had the idea to make it part of specializations; for exemple, "entertainers" should be good at music and exhibitionism and lesbian sex. "Servants" should be good at cleaning and pleasuring someone alone or a group. Ultimately, animals should use the xenophily skills and some other things; the pet cat should do rimming, the horse should do horse mating, the pig should do coprophagia… But it's in standby, because it would completely change the game balance, and ImperatorAugustus made a compelling argument against it (that I forgot).
It should be written somewhere (maybe on the rule screen) that she does it with little diligence, too little to expect that you won't give her a punishment for it. Diligence is mostly affected by mood, so have it as high as possible and try again.