Was she laying before this last winter?
Is she laying now?
It's not really a 'sex change'.
It's a hormone balance change.
Hens only have one ovary...simplistically, if it stops functioning testosterone over balances estrogen and physical characteristics can appear(male plumage, larger spurs)...
How old is this bird?
Any chance for video?
Had a 2-3yo hen crow for a few months over winter break.
Duets with cockbird every morning then she stopped when she came back in to lay.