Summer sees Tom at his favorite spot in the city, and they talk. Tom states his lack of understanding towards her actions. Summer explains that he was right about the existence of true love and that she discovered in someone else all the feelings she had never been sure about with Tom. Summer holds Tom’s hand. She says she is glad to see Tom is doing well. As she leaves Tom tells her he really hopes she is happy.

http://en.wikipedia.org/wiki/(500)_Days_of_Summer