They thought the original daughter was dead and took in the MC because when she was young, she was strikingly similar to the original girl. As she got older, she looked less and less like her so the dad became increasingly disinterested, leading to her being neglected and her status in the family dropping to practically the level of a servant. The villainess tried to get the father's attention back by acting out and clinging to her pride, but it just made her family more disgusted with her.