I have been known to seek out "fanart" of the forbidden kind

Adepta Sororitas would like a word with you…

…they agree

See how they behave around Karlach and she's only like 6ft.

The Space Marines are mostly asexual. Their humanity were purged when they become Space Marines. I would say that if a woman was put through the Black Carapace procedure, she will end up exactly like a male Space Marine anyways.