I'm the Villainess, So I'm Taming the Final Boss, Vol. 1 (light novel) — Sarasa Nagase

Villains Have Their Own Routes Too! When her engagement to the prince ends unceremoniously, details of the young noblewoman Aileen's past life come rushing back and help her realize she's living inside the world of one of her favorite otome games-as the heroine's greatest rival! However, her memory has more plot holes than bad fan fiction… and the only certainty is that if she doesn't do something quick, her death is all but assured. The hero/main-love-interest can't be relied on, so why not see what the last boss has to say?