My test as to whether a hen is broody or not is where does she spend the night. If she spends two consecutive nights on the nest instead of sleeping in her normal spot she is broody.
The way I break a hen from being broody is to lock her in an elevated cage with a wire bottom for 72 hours. I give her food and water but nothing that looks like a nest. The cool air from underneath helps break her. With most 72 hours is enough, but occasionally she has to go back in. Each one can be different. To me, this is the simplest way to approach it.
Before she starts to lay a hen stores excess fat. That's mostly what a broody hen lies on while broody. That way she doesn't need to come off the nest to eat but instead can take care of her eggs. Often I never see a hen come off the nest at all but since she is not pooping in the nest I know she is coming off. So she is not hurting herself by seldom coming off, just using fat put there for that purpose.
I'd check her for mites and lice, especially roost mites. Roost mites are scared of the dark and only come out at night, so check after dark. If she is broody roost mites are a danger.
