I had a very dominant RIR with 12 other hens (including another RIR who was not aggressive at all) and she never got better. Only worse. Pecking me, chasing the other hens, kicking them out of the nests when they tried to lay their eggs and more. I tried giving her a little peck back, and moved on to isolating her in a cage within the run for a few days, carried her around under my arm as I did chicken chores to show her who was boss. It would work for a few days then she'd get bold again. I had to re-home her and I've heard those people had to pass her along to someone else too.
I would just keep an eye on yours and make sure she's not being to mean to your EE. Hopefully she gets better but if not you may have to re-home when you get the other 5 in the spring.
I think people recommend more than 2 just because if something happens to one of them the other will be incredibly lonely. Try to keep them busy this winter with lots of roosts to hang out on, places for the EE to hide if needed and there are actually a few chicken 'toys' that can occupy them. Like a hanging head of cabbage or putting some cracked corn in one of those dog 'kong' toys.
Good luck with her. Hopefully her attitude changes for the better.