Noroi de Neko ni Sareta Akujo, Outaishi ni Hirowareru.

Overview

Lililucia, the daughter of a marquis, scarred her younger sister's face when she was a child. Feeling guilty, she continued to listen to her sister's whims, and as a result, she was molded into the kingdom's most evil woman. When her younger sister got married, Lililucia decided to stop listening to her sister's whims, but her younger sister, suspecting an affair between the princess and her husband, cursed her to turn into a cat and framed her for attempting to poison the princess. However, Lililucia, who has taken on the form of a cat, is picked up by Crown Prince Gerald, who has an excessive love for cats, and he dotes on her. If she turns back into a human, she will be falsely accused and executed, but if she remains a cat, she will die from being doted on...!? A fluffy romantic comedy fantasy about a villainous woman who has turned into a cat and a crown prince who dotes on cats. (Source: Futabasha, translated)

Source: AniList