Give her salmonella

From Create Your Own Story

You slowly infect her, and morph into a strain of super-salmonella. As she runs off on the race, you strike, and laugh. She trips, actually sliding across the dirt on her face, and flipping over. She slowly gasps, and dies of a massive heart attack. You attempt to escape, but a symptom of super-salmonella is that the body quickly dehydrates, and you dry up, and die as well.