Absolutetrash's manga / #Villain family(2)

MC gets trapped in a novel as the villain’s sister! She knows in the end all of his family gets excited, but she figures she is such a minor character, she’ll be safe if she marries herself off to a rich dude. She accidentally seduces the story’s ML instead....

MC dies and ends up in a novel as a minor character. She decides to try to save her sister from being kidnapped by hiding her, but ends up taken instead. Then she finds out that her body is not resistant to magic, so she will die unless she is by a person with divine powers. So she decides to try and marry the emperor, which would save him as well since he would not be killed by his evil son.