A Kit-Brat is a girl who is normally scene or emo or something who somehow finds it necessary or cute to wear excessive amounts of Hello Kitty jewelry and/or clothing. A Kit-Brat will almost always have a photo on facebook of herself wearing a hello kitty necklace.
Kid A: "Did you see Kelsey's new facebook profile pic?"
Kid B: "I know, what is she like 6 with all that Hello Kitty shit?"
Kid A: "What a dumb Kit-Brat."