Is She Just Bored?

So the last week or so Addi has been tormenting Payton like crazy! Today I was in Addi's room after church helping her get play clothes on for dinner at my parents when she pushed Payton into her open closet and shut the doors! Then tonight when we put her in the tub she wanted to play for a while, so Les gave her a toy and told her to make sure she kept the water in the tub. Two seconds later Payton and the floor were soaking wet. What is with that? She has never acted this way with her little sister. My mom who watches them all week while we work even mentioned that she has been pushing and taking away toys. I think maybe she is just bored! The funny thing is that if Les and I split them up for a couple hours she whines for her sister back. She really loves her, but thinks it is funny to make her scream I guess. Maybe she just needs a playdate or two. Anyone have kids they would like to loan me that would keep her busy? The neighbor said that she will be calling this week to have her over to play with her little girl, but I am worried that she may need more stimulation in her day. What is a mom to do? She is almost 4. Pre-school?