How to Survive as the Villain's Younger Sibling

Reborn as the youngest daughter of a ducal house, the narrator thinks she has landed in a sweet childcare-style romance world where everyone dotes on her, from a glamorous big sister to a watchful duke.
Then the truth hits: this is a revenge story, and the role she occupies is the villain little sister who will be targeted by that very sister, a woman who remembers being killed by her in a past life. To survive, she resolves to keep a low profile and stay firmly in her sister’s good graces. Except the sister acts strangely protective instead, tossing out lines like “Found this on the way” and “If the family kicks you out, I will take you in.”
As new wild cards appear, staying invisible gets harder, and the plan to simply avoid notice starts to unravel.