Hakyoku Yotei no Akujo no Hazu ga, Reitetsu Koushaku-sama ga Wakarete Kuremasen!

Grace is reincarnated in the world of novels as a greedy villainess. According to the story, she toyed with and abandoned the cold-hearted Duke Zane, which led to an opportunity for him to meet the heroine. If things went differently, a war would break out and Grace would die. In order to avoid a bad ending, Grace devotes herself to being a perfect villainess, but due to her serious personality, she fails to do so. Moreover, she is doted on by the Duke who is supposed to break up with her! (Source: Kadokawa, translated)