Logo text Grace Gummer had a competing offer for another show when Ryan Murphy stepped in and persuaded her to join his series chronicling the tragic romance between America’s prince, John F. Kennedy Jr. (Paul Anthony Kelly), and Carolyn Bessette (Sarah Pidgeon). “He called me and was like, ‘What is this other show you’re doing? Why don’t you do our show? I promise, it’s going to be amazing,'” Gummer recalls. “He’s very, very direct; he knows what he wants, and he’s decisive and smart as hell. So I trust him.” The collaboration was hardly new territory, as the 40-year-old actress had worked with Murphy on American Horror Story: Coven , American Horror Story: Freak Show and, most recently, the first season of All’s Fair, opposite Kim Kardashian. Still, Love Story , from creator Connor Hines, presented what Gummer describes as one of her greatest challenges yet.…