Boukun wo Migomoru Yami Ochi Seijo ni Narimashita

The protagonist is reincarnated into the world of her favourite fantasy novel 30 years ago. When she wakes up, she has become the evil woman Selena, the mother of the tyrant Xavier who will bring the world to ruin. If things continue as they are, she will be headed straight for her execution. To avoid this, she must escape the courtship of the tyrant's father, the second prince Dietrich, and prevent herself from becoming pregnant. And yet, not only is he courting her, but the first prince Volkhart, the father of the hero who is to defeat the tyrant and save the world, is also courting her...

(Source: Sorajima, translated)