Sam is a kind and supportive friend. She thinks everything sounds better on vinyl.
Sam is a senior in high school when the book and film begin. She becomes friends with Charlie at their school’s football game and quickly became one of the main influences in Charlie’s life. During her childhood, Sam experienced trauma when her father's boss molested her. On reaching adolescence and entering high school, Sam made some questionable decisions regarding relationships and sex. A pattern developed in which upperclassmen would get her drunk to sleep with her, resulting in a negative reputation and cumulative emotional torment. As Sam continued to grow, she slowly began realizing that she is worth more than what she was put through as a child, and ended her toxic cycle of sleeping with guys who didn't care about her.
However, in senior year, Sam began dating Craig, who seemed to be more interested in a physical relationship than an emotional one. In the novel, Charlie said that it seems Craig fails to listen to her, as he always seems "distracted". He also noticed that Craig more interested in himself than he was in Sam. Nevertheless, Sam stayed in a relationship with Craig and believed he was 'the One'.
Nearing the end of the novel/film, Sam realized that Craig had been cheating on her throughout their relationship and broke it off with him. This quickly led to Charlie and Sam having a bit of an unofficial relationship before Sam headed off to college.
Sam's friends are very important to her, particularly Mary Elizabeth, who helped her through the rough patches of her life. She quickly becomes very close with Charlie, who looks up to her and loves her. She is also friends with Bob and Alice.
Sam has a very compassionate and strong bond with Charlie, taking him under her wing. She helps him open up physically and emotionally and shows him new music, helping cement their gay bond. They first meet at a football game when Charlie comes to sit with Sam and Patrick. At a party at Bob's house, we see the caring side of Sam when she gets angry at Bob for giving Charlie a weed brownie and is one of the few people to not laugh at him, and then she helps him make a milkshake.
When Charlie relapses and returns to the hospital, Sam is away at Penn State college, yet she sends him letters (as she promised) and acts completely normal when he is released (which Charlie is very thankful for)
Charlie has a crush on Sam, which she finds cute. They kiss a few times throughout the story.
Patrick is Sam's step-brother, a young man coming to terms with his identity and his relations with the people around him. Sam and Patrick seem to have a comfortable step sibling bond, so much so that Charlie initially believes that they are dating.