At first it seemed like food rights, so I put out 2 separate bowls of food several feet apart. That appeared to help. However, I've witnessed the bully run halfway across the yard just to peck at one of her usual victims.
She is now a permanent resident of the smaller coop of her own.
I alternate who gets yard freedom every other day, and one day between I let them all out together under supervision.
With winter approaching, I want her to be back with the others.