"She's a bit older. I just call her Katara, 'cause she doesn't like being called Grangran." Katara, unlike Aang, doesn't embrace the future. She feels trapped by it. Ikki doesn't know as much about Katara's feelings on that as others might, but she's well aware her grandparents aren't together here. It's mildly baffling to her, but she keeps well out of it.

"Oh! Yeah, definitely add sugar!" And then she gets full authority...

Chouji, you poor soul. Because he has just given the seven year old authority over sugar, and she is sure to add as much as she can.