Kyrsten was tired of being called a "big giant mustard." So she taught Abby the word "genius" and pretended it was a negative word.
Abby: (taunting) "Kyrsten, you're a big genius."
Kyrsten: (taunting back) "Abby, you're a little genius."
Abby: "You're the biggest genius ever!"
Kyrsten smiled and said, "thanks Abby!"