With regard to @Herewegoagainandagainandagain's comment:
"The issue is pretending that agency exists in isolation from years of messaging about what women should want, and dismissing that as ‘misogyny’ avoids the discussion entirely."
I absolutely agree that many - most - sexual decisions of women are STILL being shaped by patriarchy, male sexual desire, and male aggression, rather than their own authentic sexual desire. Having a FFM threesome is indeed often pushed by the man in the relationship and the woman acquiesces because she's afraid he'll leave. The same is true for when the man pushes to open the marriage - it's nearly ALWAYS the man. I also heard about cases where the guy is pushing his reluctant wife to have sex with other men and tell him all about it (cuck fantasy). And sometimes I wonder whether some of the female subs in BDSM are trying to process rape or patriarchal abuse that was inflicted during her formative years. I also doubt that the heterosexual sex that many women are having is really the sex they want. There are many many women having unwanted consensual sex with their H because otherwise he gets grumpy and shitty and she's afraid he'll leave. Or she feels she has to engage in anal sex or kink play she doesn't really enjoy because he wants to so much. Or she gives him blow jobs so that she's spared his nightly pump and dump. Or she fakes an orgasm so that she can go to sleep (30-40% of women in hetero relationships rarely or never orgasm during their sexual encounters vs 5% of men). There are also women who are probably lesbian but would never act on it because they have internalised it as "not normal/ shameful/ disgusting".
If women really were COMPLETELY free to express their own sexual desire, I suspect their sexual world would look very very different. Women can be very sexual: unlike men, we have an organ - the clitoris - whose sole function is sexual pleasure; we have the capacity for multiple orgasms; we can go all night if we want to. Many women also lose their interest in sex at various times of their life, sometimes forever. Conversely, some become extremely sexual at times, such as when they're ovulating or just before perimenopause sets in or after menopause has arrived (because the terror of getting pregnant again is now gone). But the current sexual world of heterosexual women does not reflect much of this female sexual appetite or its fluctuations: everything is still centered on what the man wants and is shaped by patriarchal expectations of what women "should" want. What women actually want is a hindrance to this model.
HOWEVER, as @BauhausOfEliott indicates, there are women who have largely escaped this patriarchal conditioning and engage freely in the sex they want. Some want a lot of sex, some want it occasionally, some like ONSs, some want it with a partner they love, some want it with women, or in a poly relationship, or in FFM or MMF swinging.
I think we should indeed be very wary of situations that look like the woman might be coerced by the man, because patriarchy is still very much in power and such coercion is very common and destructive. But we should also recognise that some women are actually having the kind and frequency of sex they want, even if it doesn't conform to what we think is 'normal'.