What is the exposition of the book Invisible Lissa?

It's about a girl who gets on the bad side of the new/most popular girl in school Debra Dobbins, Debra excludes her from everything and suspects her for everything bad that happens then Lissa's best friend gets her in Debra's lunch time club "FUNCHY" the Lissa gets bored realizing that all the do is share with Debra and listen to her talk.