Demi Lovato was seen this week in Las Vegas where she gave a surprise performance of her new single, "Sorry, Not Sorry" at the XS Nightclub. The 24-year-old singer was sporting a black mesh crop top and matching pants and she was backed by The Chainsmokers, who were spinning a set at the nightclub. After her performance, Lovato snagged a table with her entourage of 20, which included her BFF Nick Jonas. She was also spotted chatting it up with DJ and producer Diplo.