....I know.

Daughter #1 (describing a picture of Oscar the Grouch): His face is grumpy!
Daughter #2 (bossy; authoritative): No, it's greedy, not grumpy! Say: "His face is greedy."!
Daughter #1 (obediently): His face is greedy!
Daughter #2 (dismissively bored, "you don't need to tell me because I already know"): I know.

I guess the only thing better in her mind than bossing her younger sister is making it abundantly clear that she already knows everything and anything her sister might try to tell her.