How we cite our quotes:
David nodded. "I always figured she would. She just wanted to run away because her friends were. If she stayed in the city, she'd be left all alone." (29.63)
We're not sure about Shay's motivations for rebelling against the pretty surgery (see her "Character Analysis")—and neither is David. Maybe she runs away to the Smoke just to be with her friends. If that's true, than Shay may be mostly motivated by friendship and a desire not to be alone. (And not by her desire to eat rabbit stew every day.)
"More beautiful than Shay?"
They both stood silent, their mouths gaping. The question had popped out of Tally before she could think. How had she uttered something so horrible? (32.72-3)
Okay, maybe this isn't enough to qualify Tally as Shay's frenemy. But it does show that friendships aren't always unicorns and lollipops. They can also be competitive and complex. What do you think of Tally's question here? We may not like it—but we've been there before.
"Do you think we'll ever be friends again?" she asked as they hiked toward the river, lugging their boards for the first time the entire trip.
"You and Shay? Of course."
"Even after... you and me?"
"Once we've rescued her from the Specials, I figure she'll forgive you for just about anything."
Tally was silent. Shay had already guessed that Tally had betrayed the Smoke. She doubted anything would ever make up for that. (41.19-23)
The irony is that, even after Tally has betrayed the Smoke and gotten between David and Shay, Shay does want to be friends—because when she's pretty, she no longer cares about stuff like betrayal and disappointment. So friendships can be damaged for many reasons, but they can also be saved. (Although, in this case, it's saved by brain damage. Do not attempt at home.)