Only Make Believe — Dawn Kingsbury

At first Rachel thought it was just one of Andy's crazy half-baked ideas, but the opportunity to make Stephen jealous was too tempting to pass up. All Stephen had ever done was to patronize her, and she was tired of being taken for granted by him. Soon Andy and Rachel's pseudo romance was the talk of the town. But the situation was getting out of hand. Andy was losing his sense of humor, and Rachel wasn't even sure Stephen was worth all that aggravation and deception. Boys! Why are they always such a pain?