Reiguu Sumeragi-hi wa Shi ni Modoru: Sayonara Zense, Imayode wa Shiawase ni Narimasu

A tale of rebirth in a world of nobility and magic! Leatia, the daughter of a Duke, has spent her entire life to become a worthy Empress...all for the sake of her fiancé, Albert, who will be the next Emperor. However, the arrival of Saintess Lelina changes the course of things. Charmed by Lelina, Albert decides Lelina should be Empress, and Leatia ends up as a mere consort. Overworked with excessive duties, suffering cold treatment from all around her, and spurned by Albert... Leatia ends up falling to illness, and dies carrying the pain of unrequited love. In her dying moments, she hears a voice wishing for her to be loved and happy... ...And wakes up to a second chance at life as herself again. (Source: MangaPlaza)