Could be either; too little info. Is she refusing to get off the nest? How old is she; it she at a molting age? If she is broody she will stay on her nest basically 24/7, fluffed out as to cover eggs, and give a low growl if you try to move her. They do pull breast feathers when setting.
I kind of think they put feathers in their nests. I have never let a hen stay broody, but I have seen feathers in the nests where they lay. I always take the eggs everyday and when they go broody I move them around untill they quit.