Watashi ga Seijo? Iie, Akuyaku Reijou desu!

Iris has awoken as the villainess in the world of her favorite otome game. But not just ANY otome game—one with nothing but bittersweet "Happy-Bad" Endings! If the heroine hooks up with one of her problematic love interests, the rest of the world is doomed... but if she fails, it's the villainess who will pay with her life!

Fortunately, Iris has time on her side. All she has to do is set things up so that the heroine won't go down those routes! Be it curing a fatal disease or re-parenting her possessive twin brother, she'll do whatever it takes to reject these Happy-Bad Endings!

(Source: Cross Infinite World)