This what I think changed in Toph.
...Well she has.
"I'm going with Zuko!"
"I don't know who this Jun lady is, but I like her!"
Sokka: "You saved your uncle's sweaty sandel?"
Toph: "I think it's sweet."
Zuko: (After being punched) "Ow! What was that for?!"
Toph: "thats how I show affection. "