Wait, weren't there female supermutants in FO1? I mean during the conversation with the Master you can tell him to "ask a female mutant", and the Master does have this response, though I'm not entirely sure how to reach it in game:
"{162}{Mast25}{Reasonable. One moment. Are you sure? What about the other females? It cannot be. Be.}"
https://fallout.fandom.com/wiki/MASTER.MSG
Also, I think there were female supermutants in FO2's Broken Hills, at least in the Old Ghoul's Home one of them (with the description "a dirty-looking mutant") has floats calling the other one (with the description "an annoyed-looking female mutant") "woman". Not sure where to find these text files online though, but it's easy enough to find in Broken Hills anyway.
I thought Vree's autopsy report said something about that, but apparently her cadaver's gender was "indeterminate".
Also, in Fallout 2 the deathclaw mother, Kerith, says this in dialogue:
"{115}{}{Yes. I am the current pack mother. After my eggs hatch, the other mothers will have their turn.}
{116}{}{Okay.}
{119}{}{There are other mothers?}
{120}{}{Yes, there are more mothers. Should anything happen to me, one will be chosen to take my place. The pack must survive."
https://fallout.fandom.com/wiki/Ockerith.msg
Don't know about the rest yet, but those dialogues stood out in my memory when I read your question. Hope this helps
