Dead-end villainess who makes medicine

"Just marry me for one year! I’ll offer you Cassian in return, Your Highness." Rohiriel, who lived her life branded as a villainess for the sake of revenge, was determined to destroy Duke Cassian, the man who drove her mother to her death, and his entire family. She had even prepared for exile… until she was diagnosed with a terminal illness. There was only one cure: consuming a rare flower from the Imperial Kingdom, a little every day. Without hesitation, Rohiriel proposed a one-year contract marriage to Crown Prince Yulion, and succeeded. Now the Crown Princess, she uses her medical knowledge passed down from her mother to treat the sick in the palace, all while secretly carrying out her revenge.