Akuyaku Reijou ni Tensei shita Inaka Musume ga Bad End Kaihi ni Idomu Hanashi: Shinitakunai node Last Boss yori Tsuyoku Nattemita

There was a girl who lived an ordinary life and met a sudden death. She cursed her life for being boring and dying without achieving anything. She wished for a life with a purpose, like the characters she read about in books. And so, she was reborn. In the same world as the story she loved, as a character with a proper role. But... Why did I have to be the villainess with only a tragic end! Her reincarnation was as the antagonist heroine of the protagonist. She would have her fiancé stolen by the protagonist, be bullied, join forces with the Demon King, and ultimately be betrayed and killed by him. I absolutely hated that future! In order to live and obtain happiness, I would show everyone that I could become stronger than anyone else. Even the Demon King, bring it on! (Source: Shousetsuka ni Narou, translated)