I have a Black Australorp that is brooding right now too. She has been brooding for weeks, and I was growing tired of kicking her off the nest everyday and worrying about her starving or dehydrating.
I went to a rummage sale yesterday and bought a dog crate (wire style) for $5.00, and had my husband tie it down tight on top of a couple saw horses, and made my own broody breaker. I have never done this before, the hens I've had in the past just get over it eventually, but this one seems determined to sit there all summer.
I am hoping this works. I've heard that you cannot have any nesting material in the cage, and something with a wire bottom works best. I put her in there yesterday and she seems ok, but she is still all fluffed up and clucking at me, so I know she is still crazed. (We call it "crazy girl syndrome" at my house, because it's crazy to sit on eggs that are never going to hatch!) I did put a tarp on top of the cage so I can pull it down at night, and it should keep her shaded if she needs that too.
Good luck with your hen, sometimes they do just get over it, but maybe they just need a little help other times.
Sally