You say you don't have a rooster, so you need to break her of her broodiness. Do you have a wire cage you can put her in, like a dog crate? It needs to have a wire mesh bottom, so she gets cool air on her breast and belly, to cool off. Place it on blocks for air circulation. This will take about 3 days and nights. If the weather is nice and warm you can give her a cool bath to start with, just to her breast and belly, and under her wings to cool her off.
Provide feed, water and grit, and place her in the shade where she can see her flock mates. After three days release her. If she heads straight for the nest, repeat for three more days.
Oh. You can release her during the day to poop and dust bathe, but if she goes back to the nest, put her back in the cage. You can also put a roost of some kind in the cage.
Good luck!