So, when I have to apologize for something that I truly don't believe I did wrong, or deal with someone who I really dislike, I often take the "Anne of Green Gables" approach - overdo it to the point that it's bordering on sarcastic, and giggle at them being unable to call it out without acknowledging the reality of the opposite. Think, "That sounds like a really reasonable decision!" or "You know what, you're absolutely right in every way," said with an innocent smile and sunny demeanor. You and your sister can laugh about it later, or even compete to see who can agree with the most ridiculous thing your parents say. It might help defuse them a bit, as this passes over the head of many narcissists completely. And it might help you both to get through, biding your time until you have the resources to get out. Good luck!