One mean chick

[Chickenwalls]

I've had plenty of mean girls too. There is such a thing as creating chick jail. More room tops the list. Creating sight line blockers so the chicks being bullied can go behind a little cardboard wall or some such- adding a mirror to the brooder - making a bunch more perches -- dangling treats like kale leaves -- Grab a scoop of dirt from the garden (provided it's not been treated with chemicals) and they'll instantly have something else to do (after being terrified first of course) anything to occupy the bully's energy and attention.

https://the-chicken-chick.com/how-to-reform-brooder-bully/

From the article you posted Buffalo (the mean one) has never pulled feathers or drawn blood. It seem to be more of a poke with the beak

 

[Shezadandy]

From the article you posted Buffalo (the mean one) has never pulled feathers or drawn blood. It seem to be more of a poke with the beak

That's good- it's terrible when they start hurting their buddies! As much room as you can give them - if they're in a box, consider cutting a couple of doorways and attaching another box, that sort of thing. Some of it is probably "I'm the head chick" and some of it is likely boredom that will improve once they're out in the world with more to see and do. She's learned she can make the others move, so the goal is to give them so many places to be that they can easily evade her.