I have a broody that's a lot like your's. She's constantly broody and broody jail only stops her for a few weeks (if that). I'm slightly wondering if your hen is doing what mine is doing... She mounting the other hens as though she was a rooster. When she gets on them, her wings are spread out over the other hen just like a rooster does when he's mounting a hen. Is it possible that your broody is just mounting your other hens like mine is? (I have not seen my hen injuring or killing any of my other hens by mounting them, though she easily could have drowned one of my hens had I not been there while the other hen was drinking in a water pan.) If so, this is a hormonal issue, not her being murderous.