when you guys were 5, she murdered you on purpose. now you had the opportunity too reincarnate. You were reincarnated into the perfect girl and was laceys recent age, 16.

you went too Laceys school and enrolled yourself, you were just in her class and as expected she definitely didnt reconize you. It seemed like Lacey had a boyfriend. She gave you a smile

Lacey: "Hey new girl, come sit with me and my boyfriend!"