Do you really think you’ll win this battle with your niece? If not then why in the world would you get yourself so flusterated over something that in the long run you aren’t going to prevail. Life is made up of choices and this is one you can make and live with the outcome.
I am wondering how old your neice is. Time has a way of wising people up. I used to be a liberal until about he age of 25 or 26.