Theodora and Alexandra Richards don’t get offended when people mix them up. At the launch party Thursday night for Patricia Field‘s collaboration with leather-accessories maker MCM, the look-alike blond model daughters of Keith Richards and Patti Hansen laughed when a guest confused their names. “Everyone makes that mistake,” they responded. “Once, just once!” The party at Field’s downtown pad also drew Ally Hilfiger, Emma Snowdon Jones and Brazilian model Fernanda Motta.