Who is the boss?

Sarah and Abigail do not always follow the typical birth order personalities. Abigail is a lot more accomodating than most first borns. For example, I told the girls that they needed to clean up. I asked Abigail to clean up the magnets and I asked Sarah to put away the Leapster. Abigail began to clean up the magnets and Sarah told Abigail to clean up the Leapster and Abigail said "ok". I couldn't believe my ears; the youngest is bossing the older one and the older child listens? Then later Sarah was mad that Abigail had something that Sarah wanted, so I was trying to calm Sarah down and explain that we have to share. And then Abigail comes along and gives Sarah the toy she wanted. I told Abigail that Sarah does not have to get everything she wants and Abigail said it is okay she didn't want to hear Sarah cry so "she can have it". As a mom what am I to do. Abigail is so accomodating and generous and Sarah learns that when she screams and cries she gets what she wants. Well I guess you know who the boss is in our family and it is not our oldest.