Yeah, you probably wouldn't get too many good answers to this question around here. Most likely someone will suggest that she tell the audience that the secret to life is up up, down down, left right, left right, b a, start.
Seriously, I think the best graduation speech I ever heard was a guy who said not to buy into all that crap about how new grads are ready to go out and grab the bull by the horns. He said that instead, just sit back, look at what you've accomplished, have a few too many beers to celebrate, and then after the hangover take a deep breath and devise a plan to get the hell out of your mom's basement. Of course, he said it much more eloquently than that but it was truly a great speech.