Get a wire bottomed cage and put the broody in it. You need a wire bottomed cage, so cooler air will circulate under the hen. Make sure you elevate the cage up a foot or so off the ground, again so cooler air will circulate under her. You should, I do, keep the broody buster(Wire cage), in the coop, so the others can see her, and won't want to go through the pecking order nonsense when she is released. You can put a little feed dish and water in there with her, but NO bedding. Usually I have found that it takes on average three days for them to get over the broodiness. But being yours has been broody for so long, she may have to stay in there for five or six days. Goodluck with her.
Jack