How does the settting affect what is happening in the book?

I'm reading Hate List by Jennifer Brown. The book is about this couple and how they make this list of people they hate. The boyfriend takes it seriously and shoots the people at school. He ends up killing a lot a people and he even shoots his own girlfriend. The girlfriend is trying to go back to the same school. Everyone thinks she was in on the shooting with him. The setting at the school is quite some people don't even want her there. The people in her class act different towards her.