Who is Jessica Campbell from Hate List and what is their importance?

Jessica Campbell is Garvin High School's most popular girl. She dislikes Valerie before the shooting and calls her names like "Sister Death". It is because of this that Jessica's name is on the hate list prior to the shooting. On the day of the shooting, however, Valerie selflessly put herself between Nick and Jessica, giving Jessica the chance to get away. Five months later, Jessica makes Valerie her friend, trying to pull her into the Student Council to plan the memorial and inviting her to a party. When Valerie tries to end the friendship, Jessica accuses her of being selfish because it was very difficult for Jessica to be her friend.