Ok, I think I'm slightly confused. "While she continues to be both-female." Is there a way that Herethroy can modify their gender?
Well, yes, there is one. Zie can die and get reincarnated (when and if Virid gets around to it) in a single-sexed body (if Virid sees fit to provide one). And, for those unversed in reincarnation, this will preserve zir essential personality, but leave all zir memories behind. This approach is only suitable in the absolute depths of despair.
So you see why it's not a gentle kind phrasing.
(And suitable Mutoc Corpador magic would work too, rather in the same way that a wig works to provide a mangy mammal person with full-body fur.)