Offer to take her to an amusement park for the whole day. Let her invite her friends. Take her to a place she has never been to before. Visit a university or college campus with her. Let her speak to the students there.
Many universities have welcoming committees to show perspective students around campus.
Don't forget to visit the student center. Send her to visit her favorite relative for a few days. Give her a special graduation present. Something she has wanted for a long time. Give her a slumber party night at a hotel with her friends.