First of all, make sure there are plenty of hiding places for them to get away from each other. There will be fighting while they establish a hierarchy. Once they do that then things should calm down. If things are really getting violent, like chunks taken out of each other then you can take the bully out for a few days (kind of like a "time out" then try putting her back. Any time you remove someone and put her back, take all of them out, rearrange things then put them all back. I hope this helps.