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 stepbrother, 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...?