Not wishing to worry folk, and, whilst agreeing with the earlier posts, some broody hens DO get it wrong.
It seems to happen particularly with the first clutch that the newbie broody just sits. I had a girl who I am pretty sure would have died if I had done nothing. She got lower and lower onto her eggs, and after 5 days when she had eaten no food and probably not drunk either, I found her with her head down (Food and water only a foot away).I picked her up from her eggs (no protest) and tried to stand her away from her eggs. She could not stand. I pushed the water dish under her head whilst holding her and she drank, and drank, and drank.....going on for about ten minutes. She took a little corn and could stand again after about 10 minutes. She spied her eggs and strolled back over. I lifted her again that same day when she drank copiously again, and thereafter lifted her daily to eat and drink out of sight of her eggs. She successfully hatched her eggs.
Broody again at the moment, she is getting off her eggs daily and eating and drinking by herself (Thank goodness!).
I think if the broody is taking food and fluid outside the box....great. If she won't come out....food and water in the box. Drastic measures only needed with the very rare exception.
Sandie