He Loves You Not by Tara Brown

Among her superrich friends, Lacey Winters never minded being the “poor one.” That is, until her tuition money and big dreams vanish overnight. Now Lacey has a plan to make some extra cash—a devilishly brilliant plan. For a fee, she’ll test your boyfriend to find out if he’s faithful or a cheating jerk. Her next target: a slick and sexy trust-fund playboy. Unfortunately for Lacey, his charms aren’t just legend. And before she knows it, she’s under his spell.
It was bad enough that Jordan Somersby’s father forced a spoiled “society princess” on him. Then Jordan had to go and find his dream girl—the beautiful, fun, and down-to-earth Lacey. And he’ll do anything to prove he’s sincere. But pretty soon it’ll be Lacey’s turn to prove that this is not just a game.
Because, when it comes to mixing love and deception, nothing is what it seems. And Lacey and Jordan are about to face the ultimate test.