Known to have deep feelings for Uchiha Sasuke, Sakura kept he hair long at the beginning of the series mainly because she heard Sasuke preferred girls with long hair. As she began to spend more time with him as a teammate, Sakura became concerened that Sasuke would abandon her and the rest of Konohagakure because of his lust for power. When her fears prove to be correct, she does everything she could to stop him from leaving, even confessing her love for him and offering to join him, to no avail.
Cute Sakura cosplayer! I do prefer her with long hair too. I'm not sure why she chopped her hair off, but I think it was because of one of their tests in becoming a ninja? Anyway, great cosplaying!