Dream On Dreamer III AU!Sans x Reader III

(Y/N) was born in the stars of StarFell. Unlike most, however, she was not born from a star. Rather, she was born from the darkness. Knowing this, the creators gave her a necklace to protect her from the corruption in her soul. Along with her Kumu, a (F/C) star, she ventures around her home AU peacefully. But that's all about to change. Error noticed an AU without a sans. Instead a human girl. It's called StarFell. What will happen to a peaceful AU that has never experienced Genocide?