All American Girl by Meg Cabot
Sam Madison never knew life could change overnight. But that's exactly what happens when she saves the life of the President of the United States as she's bunking off art class one night. Now an instant (if highly reluctant and very unlikely) celebrity, not to mention teen ambassador to the United Nations, Sam finds herself not only hanging out at the White House, but trying to stop herself falling for David, the President's son . . .
All American Girl, by author of The Princess Diaries Meg Cabot, is followed by the sequel Ready or Not.