The System Arrived and I'm the Villain in My Own Brother's Harem Novel?!

Eighteen years of acing exams, crushing goals, and living her best life—until a system drops the ultimate plot twist: Mu Chuan isn't just a transmigrator, she's trapped in a campus harem novel where her own half-brother is the reborn protagonist. Worse? She's been cast as the story's biggest villain. With one month before university starts and destiny closing in, can she rewrite her fate before the protagonist's revenge arc begins?