What are the motifs in Pretties by Scott Westerfeld?

Relatiopnships are a recurring idea in the story. There are several relationships in this novel that are important to the overall plot. The first is the friendship between Tally and Shay. Tally and Shay have known each other since several months before their shared sixteenth birthday. Tally and Shay pulled tricks together as uglies and Shay taught Tally how to ride a hoverboard. When Shay decided to run away to the Smoke, she wanted Tally to go along, but Tally really wanted to become pretty. However, Tally followed anyway after she was blackmailed by Special Circumstances.