I have read that ACV can affect a birds ability to absorb calcium properly, so do stop adding it to the water as GrandmaBird suggested. Honestly, even an 'avian specialist' vet tends to have more of a clue about exotic parrots than things like chickens or quail. So I doubt it would be worth your time or money trying to find a vet. You can only do the best you can and give her every chance to get better, which you are.
Hens go broody when you don’t want them to… and won’t go broody when you do.
She must have had some infection that she's managed to clear thanks to your care.