Pecking is generally caused from two things; lack of protein or overcrowding.
You could try feed them a higher protein food, like most all-flocks are around 18-20% protein. You'd have to supplement oyster shell as it's lower calcium
For coops, each chicken should have 4 square feet, and for runs, 15 square feet.
If neither of these are issues, then you may just have a bully. We don't rehome bullies. We've had a couple and they get culled.
If you do have a bully, without that hen in there, they may pick out a new victim. Just watch your flock for 15 minutes or so and you should be able to spot her.