Miley Cyrus’ dad, Billy Ray, says he doesn’t mind if his pop-star daughter doesn’t turn up to see him starring on Broadway in “Chicago.” “You never know; her plate is so full,” the country crooner, who plays slick lawyer Billy Flynn in the revival, was overheard saying at In New York and Where magazine’s recent bash at Scarlatto. “The last thing she needs to worry about is seeing her old man strut onstage,” he said. He added of his role in the musical, in which he began this month: “It’s an honor . . . I’m just some guy from eastern Kentucky who’s getting the chance of a lifetime and learning from the best.” Miley’s mom, Tish, meanwhile, was spotted in LA this week with Justin Bieber’s mother, Pattie Mallette.