I have similar, but not quite the same situations, going on here.
1. Coop flock - broody hen is in THE favorite nesting box. After she screamed and screeched for about an hour and a half, the other girls FINALLY got the message NOT to lay in her box. (They use to do that when she would get up to go get food/drink. She refused to leave after the last scream session.) I bring her food a few times a day.
She is about two feet above the floor of the coop. I wondered about how the baby chicks will get down, so I asked the previous coop owner if she had ever had to deal with that specific issue. She asked her husband and he said, "Just put the chicks on the ground." So AFTER the babies are born, I will gently place them on the ground. It probably won't take the baby chicks too long to figure out and be able to walk the ramp up and down from the nesting box.
2. Barn flock - broody hen has been forced out of her nesting box multiple times in the last month. She is sad, moves to another nesting box, and starts over. She's lasted up to 4 days before being forced out. Yesterday, she was forced out and she moved to a new nesting box and started over. I put up a door block to keep the other girls from bothering her. They took it down/knocked it down and again forced her out. So Isa moved to another nesting box and started over. AGAIN. I can't stop the "bullies" (there's a story behind their behavior - it's not her they are after - they play a game) so out of desperation and sadness for Isa, I took down a shoe box, put her eggs in it, grabbed a newly laid egg, picked up Isa, and brought her into the house. I placed her eggs on the sand in a small dog carrier and let her run around the sunroom. She drank water, explored, and eventually settled in to sit on the eggs. It appears that she has pushed 3 eggs out from under her and has selected the 10 eggs she wants to hatch out.
When she hatches out the chicks, she will stay in the sunroom for a bit longer with them. I will set up a kennel fence and make a small, shaded, protected run for her and chicks adjacent to the pasture she's use to. I may even set up a small kennel in the barn coop for her and babies.
Note - I have all roosting bars/spaces on one level in every building. Period. In the barn coop, where Isa is from, everyone is pretty much on even social status. It shouldn't be too hard to integrate her and her baby chicks.
** Is your girl completely covering all of her eggs? Is she moving the eggs around and moving herself around on the eggs during the day/evening? Is she eating/drinking?
If this was my situation, since you have a protected area, keep her and her eggs in it. Make sure there is good ventilation and provide some water and some food to her. If this doesn't seem to be working, bring her back into the house, let the chicks hatch, and then keep a barrier between her/the others for a short period of time. Things will change (pecking order) some anyways due to your girl being focused on her babies and not her social status. Have faith. Keep an eye on things.
