P.A.
Little girls do that sort of thing ,try keeping them apart more and make dates and times they can play together. Tell them if there is any arguing or fighting that the play time will be over for that day,or until the next date.make a weekly date sheet and see if that will help. Hope this helps I had a little girl with that sort of deal, they grew up to be the best of friends. To much sometimes isn't good.
P. A