I have two OEG Bantys Daisy & Maisy. Daisy is the dominant hen. I also have several other bantys. Daisy would chase all of the and peck at them if they got to close. She was very aggressive. Due to other circumstances, I segregated Daisy & Maisy in a cage without any other birds in the area. Daisy & Maisy became BFF. Although Daisy & Maisy now get along, Daisy has little to no tolerance for other banty hens. I have a white crested polish that she will charge from several feet away. The polish is twice Daisy's size, but doesn't see well.
I don't know if putting them together away from other hens would work or cause more problems, but it seems to have worked for those two. As a side note, it seems to me that in Daisy's case she is only over aggressive if the other hens are in proximity to her favorite Roo.