You could try putting the mean one in "solitaire" a crate, or fenced area just for her, for a few days to get her out of the flock. When she is put back in, she may be lower on the pecking order.
But, if she causes bloodshed, I would either rehome her, or let her swim with some noodles in the soup pot. Easy for me to say because she isn't mine.
But, if she causes bloodshed, I would either rehome her, or let her swim with some noodles in the soup pot. Easy for me to say because she isn't mine.