The Perfect Plan for a Fairy-Tale Ending

"There was a pitiful girl who cried tears of diamond and lived while being abused by her family. But a prince appeared and killed off the entirety of the evil family. And so, the girl lived happily ever after with the prince." ...That is how the fairy tale goes, but I reincarnated as the evil sister, Marcia Blick?! This damned household! At the very least, I have to escape now! But if I run away, what about my sister who will be left behind? I've made my decision! We're going to run away together! "Larisa. Let's go find that prince who will make you happy! But... Prince, why are you proposing to me? Your partner isn't me but my sister! This sister of yours will make you a perfect-ending plan!" (Source: Kakao Entertainment Corp., translated)