That servant was so stupid you need to suspend disbelief. Human rights are a modern invention. Before, poor people in constant contact with the wealthy were painfully aware that their lives meant nothing to them, that they could get rid of them on a whim and no one would bat an eye.
It's especially jarring since everyone in the family loves Rosalia so her position seems really secure. Forget the surprise stab, all it would take is one word and she'd have lost a safe and great job like an idiot.
Anyway, those ever-advancing save points are going to fuck over Rosalia, she's killing without any planning. She treats Meredy's power like a blank check for consequences, when on the contrary if they see someone dead they want alive (like the mother), that moment will be set in stone.
Here I think she's going to regret wasting most of this day since she remembered her mother's fate