Am I Crazy?

No high school student should ever have to go through the highs and lows that Riley Newman has. Her best friend had to move away due mainly to her dad's profession and her parents were killed all within a month of her birthday.
She moves around a lot, and many foster homes merely look after her for the money. All of this occurs over the course of a year, up until one foster parent becomes a little too emotionally attached to her.

Riley does what every high school student does when they are told they must attend a new school far away from home: she shows up and doesn't socialize with anyone. Her wish was that everyone would ignore her, but she has a friend group that welcomes her with open arms.

Savannah, Ashton, and Teagan are the most uncomplicated friend group at Rockville High. Savannah has always wanted to welcome another girl into her friend group because she has been the only one since fifth grade. Savannah nearly stopped breathing when she learned that there would be a new girl in almost all of their classes.

When the three introduced themselves to Riley, everyone felt hopeful for her. Riley's mood improved, and she realized that perhaps this change was necessary for her. Riley becomes more comfortable with everyone in the friend group as time passes, but the title of unproblematic is taken away from them.
Is Riley the reason everything goes bad, or was the friendship always on the verge of ending after 12 very long years?