I have heard that separating an aggressive hen in a look don't touch situation for a day or two can change this. Some folks say 2 weeks. It could be done during the day and then let everyone roost together at night. They have suggested putting up a divider in the coop run, or even using a dog crate. I have not done this, but some have had some success with it. It might be worth a try. The idea is to physically remove her from whatever position she is in and allow the others to shuffle and bond, then when she comes back in she has to work her way into the group.
I have separated Mad Hatter and have decided he will go into the fenced garden with his coop. It will not be 100% safe, but I'll do what I can to make it very difficult to get to him. It is his best chance at life right now. I hope the new circumstances, in a coop and run out of site of any of the hens, will mellow him out towards us. He is just a cockerel now, so if I can't work this out of him now, he will be a very aggressive rooster and that's not good for anyone.
Once he is on his own, I will spend a lot of time with him. He might be the first chicken I make a personal relationship with. I hope so. I really am fond of the little jerk.