I have four laying hens. Three are buddies. They sleep, eat, sun bath together. The fourth one is by herself. She is mean to everyone. I have put her in timeout in the dog crate. It seemed to make her meaner. She is 2 and a brahma bantam. One of the hens was raised with her. I have 4 bantam chicks. They are 8 weeks. I have them in a coop and run inside the big chicken run. This hen is becoming so mean. She makes horrible noise at the chicks. I ran out to look at them. I have never heard that noise before. She has tried to dig holes to get to the chicks. She rams the wire sides. She yells at the when they try to eat or drink. I don't know what to do. She is my daughter's favorite. She has lots of food, water and room. Can I get her to be nicer? Should I lock her up by herself in the small coop?
How big is your coop and run? Bantam Buff Brahma are generally a more busy breed of bantam. She sounds like she's probably dominant and is defending her territory. I would assume she will calm down after she's more familiar with the chicks. Having enough room so she can run and be a chicken will help her to burn off excess energy. In the end some chickens are more aggressive in general than others, and there's not much else you can do about it. If she's too aggressive removing her will help the others, but not her.
She is in a 20 × 20 run with a 10× 5 coop. It's her and 3 other hens. She is being mean to other hens as well.
https://www.backyardchickens.com/threads/mean-mean-attilla-the-hen.1314433/ If you read this thread you'll find tons of great ideas, opinions, feedback. Very similar situation to yours.