I'd Tell You I Love You, but then I'd Have to Kill You: Gallagher Girls Book 1 by Ally Carter

Cammie Morgan is a student at the Gallagher Academy for Exceptional Young Women, a fairly typical all-girls school - typical, that is, if every school taught advanced martial arts in PE and the latest in chemical warfare in science, and students received extra credit for breaking CIA codes in computer class. The Gallagher Academy might claim to be a school for geniuses, but it's really a school for spies.Even though Cammie is fluent in fourteen languages and capable of killing a man seven different ways with her bare hands, she has no idea what to do when she meets an ordinary boy who thinks she's an ordinary girl.Sure, she can tap his phone, hack into his computer, or track him through town with skill of a real "pavement artist" - but can she maneuver a relationship with someone who can never know the truth about her?