I have a large mixed flock including several cockerels that free range. So far I've had 4 hens go broody and rear chicks, some multiple times all within the flock and even the low ranking broodies have managed to defend their chicks or keep them out of the way of more dominant hens (I've never had a problem with cockerels bothering the chicks and only very rarely scuffles with hens) though I do think not being penned in means that the other hens have space to go off foraging and therefore don't get frustrated and look for trouble.
I keep an old sideboard in the hen house that I have modified for use as a brooder or infirmary depending on requirements. I lock the broody in so that she cannot be disturbed by the other hens and let her out once a day to relieve herself and stretch her legs. The broody nest is quite dark which they like and when I open the door, the light seems to stimulate them to get up and take a break and get something to eat. I close the door whilst they are out so that other hens can't lay in their nest. I do chores whilst she is out so that I can supervise her break and then after 15-20 mins, when she heads back towards the hen house, I open the brooder door and she climbs back on the nest and I shut her back in. The first few days she sometimes goes for the wrong nest, especially if I have initially moved her nest but if you make sure all the other nest boxes are empty, she will select the correct one with all the eggs in. This way she still has some contact and interaction with the rest of the flock on a daily basis but gets the peace and quiet of a safe place whilst she broods. I do put food and water in the sideboard with her, just so that she has it there if she wants it as they do lose condition brooding and low ranking hens have a harder time getting the necessary food in the short space of time they are active each day.
With your set up, you could easily barricade her into that corner where she already has her nest. and just let her out once a day like I do. You could place a removable grill or mesh across the front and I would also fix a cover over the top as they prefer to be in a dark secure place and it would stop the other hens possibly climbing in from above.
Once the chicks have all hatched she may wish to leave the nest site with them anyway. Mites and such can build up in a broody nest, so they often like to move the chicks from it as soon as they are able. She will probably find a safe place somewhere else on the coop floor but you could move her to a small cage in there for a few days until the chicks are fully mobile and the other hens can get used to them.
I wouldn't give her more than 8 eggs for a first time especially at this time of year. Good luck with her. The only real worry I think is that if she has already been broody for so long, she might give up before the chicks hatch.
Watching a broody rear chicks is the best chicken TV ever. I highly recommend it.
PS. I find it a good idea to dust the broody nest with DE for mites before I set the eggs as the constant warmth from the broody can attract them.
PPS. Be warned....Broody poop absolutely honks!
Edited by rebrascora - 10/12/15 at 11:35am