lemmy.blahaj.zone has a decent amount of women and both their admins are women, it's not a "women's space" as one would describe since everyone is welcome there but it's probably the closest thing one would describe as an instance "by women for women". I am obligated to mention that it is a queer instance and that many of the women there are either trans themselves or strongly supportive of trans people, and do not tolerate transphobia or anti-LGBT sentiment (including refusal to support LGBTQ people) at all.