Akuyaku Reijou nano de Last Boss wo Kattemimashita

Avoid the bad ending at all costs! When her fiancé breaks up with her in front of the entire student body, noblewoman Aileen d’Autriche is devastated—or she would have been, if that wasn’t also the exact moment memories of her past life came crashing back! Turns out, she’s been reborn as the villainess of a dating sim... and according to the story, she’s slated to die at the hands of the demon king in three months! But Aileen’s already got a plan: Step one, get Demon King Claude to fall in love with her. Step two, live!
(Source: Yen Press)
Note: Chapter count includes 4 extras.