Insatiable by Cari Quinn

Rachel and Shawn have been friends all their lives. Growing up in wealthy, privileged households, it has always been an exception that the two would grow up and get married, but Rachel does not want that to happen. Shawn has always had feelings for his best friend. He's looked after her all his life and always held back his true feelings. But when he finds out Rachel is going to New York to see her ex, he decides it's time and follows her.