Here's what you do.
First, have a buddy tape the game, so you'll be able to watch it whenever you want. Next, take her out to dinner to whereever she wants to go. Don't look at your watch and don't talk about the game. Don't worry about missing the game, it's just a preseason game. When you get back, turn on the tv and see if you can catch the end or some highlights. If she realizes that you missed the game for HER, it may pay off for future big games!