Theory on Raquel's hatred of Camila
Watching it, I thought the movie was building up to a reveal that Raquel disliked Camila because Raquel knew/suspected Camila to be the product of the mother's affair with someone other than the dad - that Raquel had an antipathy toward Camila because she was not really/truly a part of the family that Raquel was so devoted too.
The daughter, Camila, is the oldest and it is mentioned Raquel joined one year before Camila was born - putting Raquel there at the crucial affair time.
Also, this theory has the added benefit of explaining why Mom doesn't just fire Raquel: because she knows Raquel knows and if she fired her, Raquel would spill the beans in revenge.
Even if the filmmaker wasn't intentionally trying to present this, I think he's created a film that really raises the question of why the mom wouldn't fire Raquel. I really thought that any mother, the second after she saw the maid scratched one of their child's faces from pictures, would have fired them immediately. Also, with all the other trouble Raquel caused, I really think the movie created a mystery as to why she wasn't kicked out of the house.
Anyway, I have to wonder if my theory wasn't some "backstory" the director told the actors to inform their behavior, but kept unsaid in the film.