Hanna and Mona Vanderwaal decided to become skinny and pretty before the next year 's cheerleading tryouts .
Mona Vanderwaal is a girl that Hanna and her friends used to make fun of for being dorky .
Hanna and Mona Vanderwaal , a girl that Hanna and her friends used to make fun of for being dorky , decided to become skinny and pretty before the next year 's cheerleading tryouts .