For as much as a shitbag moo is, I can't help but feel bad for her. Her dad's a fucking douchebag and loser that doesn't deserve being a parent or in his daughters' lives if this is how he treats them.
So he was often absent from her life (at some point, he even separated from Mariah's mother and impulsively got married to a much younger woman in Lebanon, only to eventually go back to his previous wife), made Mariah and her sister compete with each other for his attention, withheld affection from them for being "fat", encouraged them only when they exercised, and never acknowledged any of Mariah's accomplishments that didn't involve his own interests (he was a bodybuilder).
Not that Mariah needs to be defended (she's nasty on her own, and is old and financially independent enough to seek psychological help; her sister seems to be mostly normal, though abusive parents sometimes treat one of their children better than the other), but I really think that it can't be understated how much Mr. Mallad failed as a father and deserves the humiliation brought by his daughter Mariah.