In 1989, a 39-year-old executive found herself at a crossroads. After 17 arduous years of climbing the corporate ladder at Vogue, she lost the editor-in-chief position to a rival, Anna Wintour. One day, while struggling to find the right gown for her upcoming wedding, she spotted a business opportunity: designing dresses for others. Hesitant, she wasn’t sure she’d make it: “Maybe it’s just too late for me,” the executive wondered. Still, she took the plunge, and one year later, she opened a bout...