At splashy weddings, charity balls and all the right restaurants, she hobnobbed with San Francisco’s moneyed elite—and made lasting allies who backed her at every stage of her political career. SAN FRANCISCO—In the summer of 1999, in the monied Napa Valley north of here, a bejeweled bride rode sidesaddle on a speckled horse into what the press would label “the Bay Area’s version of an outdoor royal wedding.” The lavish nuptials of Vanessa Jarman and oil heir Billy Getty—replete with red carpet, hundreds of flickering votives, and “a fair amount of wine,” according to one deadpan attendee—featured a 168-person guest...