AMANDA Hearst (above) is now dating Alejandro Santo Domingo, son of one of Colombia’s richest men. They arrived together at the Best Buddies fundraiser Friday at the Water Mill estate of Amanda’s mother, Anne Hearst, and Jay McInerney, ParkAvePeerage.com reports. Amanda, who starts work this week at Marie Claire, broke up last year with Winston Lapham, son of Harper’s editor Lewis Lapham. She met Harvard-educated Alejandro early last year at the wedding of his brother, Andres Santo Domingo, to Vogue’s Lauren Davis.