Why would the maids and butlers, as well as the parents, side with the sister? She's caused all their problems, she's rude in front of them, they're scared of her, what power does she hold over them? Why would they prefer her over the MC daughter?
Like, why did they kick out the MC's maid, when the evil sister was clearly gloating about doing it in front of the rest of the staff? This seems goofily written, though I do enjoy simple revenge stories, so whatevs.