“It was the craziest overnight five-year success story ever.” —Leigh Dunlap Leigh Dunlap went to film school at the University of Southern California to study screenwriting, which led her to a job selling socks at Fred Segal and eventually to an assistant’s desk at a Hollywood talent agency. That’s where she really learned how to write—while reading hundreds of scripts sent in for actors. Her first screenplay, A Cinderella Story, with Hilary Duff, was made by Warner Brothers. Since then...