Hi I’m looking for the title of a Korean novel where Mc is rlly smart and works hard. She’s engaged to the crown prince but overhears his friends and him talking about how her younger sis is prettier or something. She breaks engagement but turns out he was in love with her. Guy who recommended sis was in love with her too. She becomes a mage/wizard or something. Her sis who was supposed to help crown prince with MC in beginning actually likes him.