The eyes of Susanna (Suni) Agnelli, as befits a scion of Italy's Fiat-founding first family, could at the same time cast an imperious patrician stare and display a wry twinkle. Larger than life in multiple realms, Agnelli, who died May 15 at 87, was a best-selling memoirist (We Always Wore Sailor Suits was the title of one), mother of six, advice columnist, politician, diplomat and innovative philanthropist.
While her brother Gianni ran the car company founded by their grandfather, Suni drifted into politics. In 1974, she became the mayor of her Tuscan coastal village in an effort to save it from...