Why?

Lilly had already spilled water all over herself in the car after refusing the sippy straw cup. We stopped to eat and were ready to get back into the car. I was trying to negotiate how to bring the left-over milk with us knowing she would demand the individual serving sized botte with the highly spillable top. I was explaining that we didn't want the milk to spill in the back seat so we were going to put it in her cup with a lid. She takes a big drink of milk and says, "Why????" which causes the milk to spill out of her mouth and down her chin. I think I just proved my point. I couldn't help but laugh. Not surprisingly, she took a couple more drinks and let it spill out of her mouth. I know I shouldn't have laughed, but sometimes I just can't help myself. I'm finding it's a lot harder for me not to laugh at home than trying not to laugh at inappropriate/funny behavior at school.