So we've got 3 bullies and 3 well behaved, and the bullies only pick on one of the well behaved so far?
Who are your "originals" and who are the newbies?
I'd start with your bully hen, as she probably has the best chance of success. Make her the penned, ineffective outsider so she can't follow through on any attacks. Have them all eat near her pen, drink there, make shady spots nearby so it's a really good congregation area. Do that till she quits posturing/fluffing/growling. It might be weeks, don't rush. Then you can try letting her loose, but only with multiple feed and water stations and lots of ring-around-the-rosy hiding spots and perches so if she gets aggressive, your victim can give up but still get away. Bully may always be a top of the pecking order kind of gal, but there needn't be any serious injuries and they usually stop the aggression once they've settled their hierarchy.
So far as the roosters go... I don't even have hatchmate brothers that won't eventually come to dire blows. Rejected males often violently take what they want from a hen and I've seen hens who want to move up the ladder literally attack helpless other hens while pinned down by such a male. A bully will absolutely feed off of the weakness of a hen who is already too submissive/cowardly due to frequent unwanted rooster attention. If you're serious about keeping all the boys, I hope it works out but I don't have any useful advice there. Mine just don't get along without fences.
Best of luck! Let us know how it goes!