letty was a nurse in her past life, and like usual her engagement to the prince was annulled by the prince himself. However, when the King collapses Letty receives a past memory of when she was nurse to save him (then gets the rest of her memories back). Deciding to make changes, she saves the country from epidemic and etc.
Rebirth of the Villainess: The Life of Letizia after the Engagement Annulment