I like Poultry Nutri drench TSC carries it.
Also cat kibble fish based is great protein for them when molting and will also help keep her fit while brooding. along with reg feed of course. I give mine dog kibble salmon and pea and dried mealworms as extra protein[ I haven't any cats]
Sounds like she is broody so just keep and eye on her. Usually they pluck the feathers in their chest to line their nests, the downy ones, If you have some poultry vitamins put some in her water. Usually they molt after being broody .