Gwen Stefani was the third wheel on her pal Kate Beckinsale‘s date with husband Len Wiseman the other night at Condé Nast Traveler’s party at Aria in Las Vegas. Stefani sat with the couple while her own husband, Gavin Rossdale, performed an acoustic set for guests. “It was kind of funny — she was sitting there while they were cuddling and smooching,” our spy said.