My Lady, Please Become My Heroine! summary:

After dying from overwork in her previous life, Beth finds herself in the world of a novel she was reading. While she’s reborn as an unimportant side-character, she ends up working for the house of the novel’s villain, the strict Lady Claire. There, she witnesses first-hand the abuse and negligence a young Claire goes through, and decides to stop her from becoming a main character!