She Became the Wicked Sister-In-Law of the Heroine

‎My death was already unfair but I can’t believe I’ve transmigrated into this disgusting affair-glorifying novel!
*
Because of her father’s affair, she grew up abhorring the idea of it and was disgusted by anyone who committed such ‘heinous crimes.’
Her mundane life was laborious but fruitful, however, the novel she chose to read on her break turned out to glorify the affair between the female lead and the male lead.
She was furious at the novel’s ending, so much so that she actually died! Wouldn’t be strange even if she won the Darwin Award…
When she opened her eyes, she was in the novel in question, .
She possessed the body of Lucia. She was now the sister-in-law of the heroine, Rosalyn.
She became the younger sister of Seamus Chase, a man of misfortune who took his own life after struggling to somehow change the mind of his cheating wife.
*
I don’t want poor Seamus to have such a miserable ending, or to see myself punished for being a villain.
But most of all, I hate seeing people who have had affairs have a happy ending.
It seems the God of this world has the same idea.
In this world, one could boast about their adultery, as it was a virtuous deed. Those who cursed adulterers were deemed unfashionable and ignorant.
But she has been given an oracle to fix this crazy world.
It was unexpected to become a saint all of a sudden, but to ruin the happiness of the female lead and the male lead, first let’s reform this crazy world!
Oh, of course, in secret.