No More Boys — Charlotte White

When flirtatious Molly decides she's through with boys forever, her best friend Kristi bets her that she can't stay away. Even Molly wonders if she can survive the whole summer without a date. Just as her determination weakens, she finds an unexpected ally - Kirsti's handsome, idealistic brother, Ben.
Ben is just like an older brother to Molly. But when he helps her get a job at the public day camp where he works, she sees a side of him she's never seen before. And in spite of her bet with Kirsti, Molly feels herself drawn to Ben. Could she be falling in love with him? And what will happen if Kirsti finds out?