I have a nasty mare like this. She just plain isn't happy until she's kicked everyone's *ss. Usually, it's not bad - just a show of how big she is, though there have been a few times where she's kicked them pretty badly.
What I always do is just to let them share a fence line for a few days or a week, then introduce them - just the 2 of them, in good strong fencing, and let them come to an agreement of their own. If you keep the paint, it will happen sooner or later, and as far as I go (personally) best to just get it over with. If your situation is such that you can keep juggling them, go for it, but I just find it simpler to let them work it out.
Ask Often, Demand Nothing, and Reward Generously.