Is Blanca meant to be a sympathetic character?

I just rewatched her backstory and, while badass, I don't really think Blanca was justified at all in terrifying the old lady into submission like she did. Like... the old lady was annoying and needy, but considering it was her paid job to look after her, I don't think it would be unreasonable for her to suck it up and act reasonably. Making someone's last few months/years submissive and scared just feels gross to me.