C.C.
Well... having the instinct to go for the jugular is not something you should convince her to give up, in my opinion. A strong desire to succeed will serve her well in life. Teaching her that winning isn't the point is not resonating with her because she knows you're condescending to her! Winning IS the point. BUT, the flip side of that is that no matter how good you are, sometimes you will lose, and when you do, you shouldn't be a jerk about it. THAT's what you need to teach her. I would do that by reminding her before the game that if she wins, she should be a gracious winner (let her opponents know that she appreciates their sportsmanship and/or thank them for playing with her), and if she loses, she must remember that there will be a "next time," a chance to redeem herself, and though she may be disappointed, that she will be punished if she throws a fit. Then play the game and see how it goes! It will be a work in progress for a while, but she will get it eventually.