Toxic - Natasha Devon

Llewella has straight-A grades, a lead in the school play, a prefect badge, a successful blog and a comfortable life. Despite this, she feels like a brown, chubby square peg at a school full of thin, white girls. She's never had a best friend. Could the new student at sixth form - glamorous, streetwise Aretha - be the one?

Llewella and Aretha get tight, quick. Before long, Llewella is following a diet Aretha has designed for her and has abandoned her own passions to dive headfirst into Aretha's world. She's determined to be the most loyal, greatest friend she can be, even when Aretha says and does things which make her feel the opposite of great. Even when the anxiety disorder she thought was cured starts to re-emerge.

Isn't that how friendships work?