Having a very similar issue with my flock of 11. I have a cockerel, he's big but he's not old enough or confidant enough to feel comfortable stepping in with the fighting. I'm going to try this method and see if it helps. Fingers crossed!We had this issue briefly. Here's how we solved it. Take the bully out and put her on the floor in a wire dog crate but keep the crate in the coop so she is still part of the flock, she just can't bully anyone. Keep her there 3 nights, then watch to see how she does. If she bullies again, repeat 3 more nights. We did not have to repeat a third time. She had an attitude adjustment. No more problems!