The Sponsored Underclassman Wants to Replace the Heiress, but the Vicious Supporting Actress Defies Fate

The junior student I sponsored barged into my engagement party and ran off with my fiancé. She said this world was just a book, I was the villainess, and they were the destined couple. She planned to use the System to send me to prison and take over my life? What a ridiculous fantasy. How could someone who transmigrated into a book possibly defeat an heir carefully raised by a powerful family?