Idk if any women have used it, but I am sure it could be helpful and has minimal side effects. That being said, there are likely other drugs that would be more effective like dutasteride, oral minoxidil, bicalutamide, estradiol, etc.
As a first choice, no need for women to expose themselves to all the uncertainties of RU efficacy or safety when they can tolerate systemic T reduction, unlike men. The whole point of RU in men is to keep the effect as local as possible
e.g. low dose oral spironolactone is an option that (most) men don't have
Also, many women don't respond to the same androgenic-reduction based treatments that men do - but to the extent that their hair loss is mediated by androgens, then yes you'd expect RU to "work" too
I've been using it for about a month now. Been using minoxidil and finasteride for a little over a year (yeah, I'm a woman). I've also tried spironolactone. My testosterone is only slightly above range. I don't believe I have PCOS though, my cycle is regular. Should I be using RU? I don't know but I'm doing the nuke approach. So far it seems like it helps with shedding but it's also winter and I shed less this time of year. I guess I'm going to have to give 6+ months to see if it works, it's not a big deal since it's mixed with my rogaine.