Nostalgia barged in like gangbusters. What brought it on was a brief article about the most charming and enchanting of young women, Nancy Olson. Seventy-two years ago, she was in that rare gem of a movie, Sunset Boulevard, playing the rosy-cheeked screenwriter who was the love interest of William Holden, the writer who was handsome but entrapped by Norma Desmond, aka Gloria Swanson.