Not all the Nephilim were male, it seems. Just as human offspring aren't all male, neither were their Fallen counterparts. And some of the Fallen Females were . . . well . . . pretty hot.
Isis, for example. She appears to have been an original "angel," worshipped as a goddess by the Greeks, Egyptians, even many Europeans (the name of France's capitol city, Paris, derives from her name [Par-Isis, meaning variously "City of Isis" or "Through Isis"]). Was she indeed a Nephilim, an Anunnaki first-visitor, or the spawn of Nephilim & humans?
Two things to remember:
1) The original "Fallen Ones" were referred to as "Nephilim" in the Old Testament, but so were their giant, hybrid offspring resulting from mating with humans.
2) Isis taught humans, especially females, all kinds of secret and/or forbidden skills - one of the behaviors for which the Nephilim were so infamous (along with consorting with humans and siring the giants).
More on Isis, female Nephilim, The Watchers and etc., coming soon!