03/07/1994 at 01:00 AM EST
Call them romance heroines of a certain age. Scarlett O'Hara, 28 at the end of Gone with the Wind, advanced squarely to 35 (and won back Rhett Butler) in Scarlett, Alexandra Ripley's best-selling sequel to the Margaret Mitchell classic. The author, however, well understood how lightly the patina of time would be allowed to alter the coquette's complexion. "No reader wants Scarlett to get even crow's-feet," says Ripley, 60. "And no sagging anything!" And what about Francesca, the 45-year-old farm wife who falls for a dashing photographer in Robert James Waller's The Bridges of Madison County? At Francesca's time of life, says Waller, 54, "you don't always expect thunder and lightning. But if it comes, so much the better."