Akuyaku wo Yametara Gitei ni Dekiaisaremashita

Reincarnated as the duchess from a novel she wrote in a previous life, Lelia finds herself the villainous character who bullies her cold, expressionless, and beautiful brother-in-law, Rudius, to death. In order to avoid the worst, she takes good care of her brother, but for some reason he presses her for help...?