Akuyaku Reijou desu ga Kouryaku Taishou no Yousu ga Ijou Sugiru @comic

Mystia Aren is the daughter of a noble family who just started at high school. She's surrounded by a group of adoring classmates and her charming fiancé. Everything seems perfect. Except that this world is actually a dating sim called "Kyun Love," and she's destined to become the main character's evil rival! Mystia is determined to do everything she can to avoid her fate but it's not as easy as it sounds. Especially when all the boys keep falling in love with her! (Source: Tokyopop)