She's a rainbow

Adèle has never liked being the center of attention. When she starts receiving love letters in her locker, she suspects a bad joke. Gravitating between her passion for painting, her only friend Elba and her obsession with actor Jerrald Griffith, she tries to blend in. Victim of bullying for months by Ezekiel, it is when he makes that "too much'" joke that Adèle slaps him in front of the whole class. Sent to Principal Schroeder, the punishment is severe: she must tutor the school's star field hockey player three nights a week. The principal, touched by the young woman's family situation, offers her weekly meetings to help her come out of her shell and present herself as a father figure. She accepts, moved by such concern for her. But are his intentions really honest? Why did Ezekiel start to hate her overnight?

Who is this S. who sends her these letters that put a little rainbow in her rainy days?