SAN FRANCISCO In April, Wan Ling Martello, the head of Nestlé in Asia, found herself seated across from Arianna Huffington, an Uber director and a founder of The Huffington Post, at the Union Square Cafe in Manhattan.Over dinner, the two women who had met just a few months earlier chatted about a food recall that Ms. Martello had handled. As Ms. Martello described her salvage and recovery efforts, she said, Ms. Huffington began listening more closely. Ms. Huffington then wondered aloud whether Ms. Martello would be interested in helping Uber, which was dealing with a string of scandals, before whipping out her phone to call people at the ride-hailing company.Less than two months later, Ms. Martello had joined the board.I did not expect to be asked about Uber at that dinner, and I dont think it was on Ariannas agenda, she said. It was only their second meeting. The whole meeting was casual: Lets just hang out.Recruiting Ms. Martello is the sort of swift, behind-the-scenes power play that has propelled Ms. Huffington to become Ubers most influential independent board member. In the 14 months since she joined the board, Ms. Huffington has acted as the public voice addressing the companys workplace scandals, talked to employees and helped woo executives. She has also become one of the closest confidantes to Travis Kalanick, Ubers chief executive.