Possession by Elana Johnson

Vi knows the Rule: Girls don't walk with boys, and they never even think about kissing them. But no one makes Vi want to break the Rules more than Zenn...and since the Thinkers have chosen him as Vi's future match, how much trouble can one kiss cause? The Thinkers may have brainwashed the rest of the population, but Vi is determined to think for herself.

But the Thinkers are unusually persuasive, and they're set on convincing Vi to become one of them...starting by brainwashing Zenn. Vi can't leave Zenn in the Thinkers' hands, but she's wary of joining the rebellion, especially since that means teaming up with Jag. Jag is egotistical, charismatic, and dangerous--everything Zenn's not. Vi can't quite trust Jag and can't quite resist him, but she also can't give up on Zenn.

This is a game of control or be controlled. And Vi has no choice but to play.