its possible she fears the mc´s personality will become like that of the Townspeople, the female cook in the manor could kill with her gaze alone not to mention her constant yelling, lily certainly was like a mother to mc and his sister and with the rape of the sister the only remaining Family for both of them, the siblings have treated her with love and the mc could become the man that she longs for to love and to be loved the thought to lose this is terrible for her
and the mc could become a breeding bull, Charlotte Lady Hales daughter was the last natural birth, after that first stillbirths than infertility maybe a curse from the native´s for the Massacre on them the corpses on the ritual stone in the village hut give no pretty picture, with the mutated animals and the people that could become crazy from the fruits or other food with this purple veins, the purple Fog in the night and in the cave in the form of a skull, above all the siblings and lily are the first new blood in years
the whole island gives a Lovecraft/Eldritch/Cuthulu vibe with a pinch resident evil village and creepypasta, the silhouette from the beast in the woods with the native girl from afar looks for me like mr. widemouth, could be a Wendigo