Yes, this is rather specific sex kink kind of wish I wonder is there much. If not, perhaps I should double or move this to story ideas.
So, just like the title says, there's a (much) older woman who takes quite a lot of initiative to fix sex life of a (young) woman. They may or not be related, and may or may not have sexual relationship between them, and I rather expect at least sizable part of the younger woman's sex to be heterosexual. Also, D/s relationship between the women is not what I want, although limited, mostly psychological elements of that may be tolerated.
The catch is, that to the contrary of more traditional expectations, the older woman is not so much interfering and controlling girl's affairs than encourage and teach her to explore and actively create situations for her to exploit, possibility manipulating, but without too much coercion.
It could be (grand)mother or other relative pimping out her (grand)daughter, possibly for ulterior motives, or even just personal entertainment.
It could be teacher or other figure of authority fixing a pair of students, believing they do a good thing.
It could be a wife training a mistress for her husband, or son -- as I would rather prefer main pair of lovers to be of similar age.
Or, for more specific example, a pair of students who otherwise wouldn't look at each other are sent by the school to aid an old lonely woman as part of some kind of social service, end up spending much more time with her they expected and having sex if not on her insistence then encouragement.
Or, imagine Dickens "Great Expectations" retold with Miss Havisham as perverted voyeur who encourages Estrella to sunbathe nude, and that's just for starters.
It could be told from pov of the 'fortunate' guy who finds himself to be one of the targets of the woman, falling for, unwittingly using, but then revealing, observing and evenentually fighting the manipulation the girl is under.
Or it could be from the pov of the girl, possibly slowly realizing the manipulation she's under, exploring, exploiting and eventually subverting it for her own goals.
Or, well, the possibilities how similar situation could be explored is quite endless.