Well, it seems Ava is trying to assert her independance just as much as her brother now. She does very well with the sipper cup, so we keep one of water, out for her.
Today, I placed the cup on the chair next to me and Ava came over to play and drink. At one point she placed the cup on the computer and I moved it and said "No". While her cup is pretty leak-proof, I didn't want to take the chance that it would leak and damage the computer. Ava lookde right at me and smiled, then placed the cup right back on the computer. She and I moved the cup back and forth between the chair and the computer a few times, before I moved the cup further away and she became tired of the game. It was very frustrating, as she knew exactly what she was doing, the little goof.