But just look at her! She's got those tiny, almost feral pupils ready to stare into your soul and violate it, she's got that bright and cheerful outer shell to make you drop your guard, and she has that true inner darkness covering her eyes ready to burst out at any time and devour you. Definitely yandere.
"Come on, drink this! You like vegetable juice, don't you? I decided that you must, right now" is what she said if I remembered correctly. That was terrifying.