Nokori Ichinichi de Hametsu Flag Zenbu Heshiorimasu: Zamaa RTA Kiroku 24Hr.

Alexandra is the daughter of a duke in the Kingdom of Tarraconensis. One day, she suddenly realizes that she is the villainess in an otome game, just one day before the story's climactic event! She knows that she'll be denounced and her engagement annulled the next day, but she won't be condemned so easily! She will show her accusers what she's really made of! With only 24 hours left, Alexandra must fight to overcome a desperate situation.

(Source: ComicWalker, translated)

Note: Includes two extra chapters and an epilogue.