Is she on eggs or just on a nest being broody? Are you sure she is actually broody not just being cranky (one of ours did that for a while)? Is she on a nest that is a good size and on the ground (she could be trying to find one that she deems safer for babies to hatch in)? Are other chickens giving her a hard time (pecking her, or pushing her off)?
Well, there are 2 parts to our coop. And she comes off her nest on one side then goes outside then foes to the other part of the coop. And, I positive she is broody. And some of the smaller chickens give her a hard time once in a while.
I agree. You should seperate her. That just happened to me. Mine would leave her nest to take her potty break and another hen would then take her nest (usually lay an egg in there, which I would have to take out) and then my broody would get confused I think and find the nest closest egg to sit on. I caught this happen a couple of times and moved her back to the correct nest. Finally, I moved her nest so that she was secluded from the others. She was happy and so far has hatched out two chicks.