I have had success with putting the broody in a smaller pen but with company, another broody, an extra rooster, someone who's from the same group, so there's no real fighting, the constant squabbling, or attention from the rooster keep her from setting down. I find that one broody hen can quickly give other hens the idea, and before you know it you have half your flock broody, they are disruptive to the whole flock, of course if they are banties, then they're all broody, and I just let them go or put them to work hatching eggs.