I have been looking for this book since I was ten.

Hello, I was hoping for some help in finding the title of a book I read in one sitting in the fifth grade. The story is about how "mother nature", grown angry with human destruction, decides to reset the Earth by burning down everything manmade, as well as most of the human race. The main character is a teenager or young adult girl who goes through the fire at a summer camp. The only remaining survivor is a guy who she had previously butted heads with, but they have to travel in the same direction to find their families, who may or may not be alive. They make their way across the United States, and are surrounded by species of plants and animals that were previously extinct.

It's not that this is the best book in the world, but I have wondered about what it was called on and off for such a long time. Any help would be appreciated.