Marella Agnelli, an Italian aristocrat, art collector, socialite and style icon, died Saturday at her home in Turin, Italy. The widow of the late Fiat tycoon Gianni Agnelli was 91. The daughter of Neapolitan aristocrat Filippo Caracciolo di Castagneto, and of an Illinois-born mother, Margaret Clarke, Marella Caracciolo was born in Florence in 1927.