I said, "Share!"

In a desperate attempt to keep Karoline awake while I dropped off boys at soccer practice late in the afternoon, I bought Katie and Karoline a strawberry milkshake to share. They were sitting side-by-side in the back of our full-sized van. After several peaceful moments up front with Brad Paisley, I heard, 

Karoline: MOM! Katie won't share!

Mom: Katie, I bought a big one for you both to drink. Please share with Karoline.

Katie: I really don't want to share. 

This surprises me, but communicating is difficult for me from the front of the van, so far from them and unable to see faces. I press on. 

Mom: Katie, really, you need to share with Karoline. Give her the drink.

Katie: She has the drink.

Mom: She does? (Now I'm utterly confused.)

Katie: I don't want anymore; she can have the rest.

huh?

Karoline: No, you have to have more. I'm sharing! I can't be a good friend if you don't have more. MOM, KATIE WON'T SHARE! MAKE HER SHARE! You all just won't let me be a good friend. I'm never going to get to heaven with a sister like this.