P.S.
My kids are 5 (girl) & 3 (boy) & they have been sharing a room for a few years. They are just fine with each other but the quarrels are still there being siblings. I would give it a few weeks before seperating them again. Maybe give your daughter a few things that she can choose like a special comforter or decorating item. They are young enough that they do not need seperate bedrooms. Good luck! Try to be patient it is just a new adjustment you all have to make.