Friend is really upset over this, what should she do?

Hey guys, I have a friend who has been in a relationship with her highschool sweet heart for 3 and a half years. Needless to say she loves the guy to death! So he didn't want to go to prom, and (Long story short) they didn't go, and she did want to go. She goes to a different school. Her gradnight was a few weeks ago, and sadly she didn't get to go due to lack of funds. Now his gradnight is comming, and she is a upset because he says he is going, and she is happy for him but she says it's not fair that he gets to go to gradnight and no matter how much she wanted to go, he didn't take her to prom. What can she do? She doesn't want to stop him from going because she says he deserves to go, but I think it's not fair she didn't get to go to her senior prom and he is sure as hell going to his gradnight.