Hailee Steinfeld and Niall Horan didn?t do much to squash those pesky dating rumors on Saturday, February 17, when they attended a Backstreet Boys concert in Las Vegas together. They were spotted laughing, dancing and singing along at the concert, held at the Planet Hollywood Resort and Casino. A week later, Horan attended a birthday party for the ?Starving? songstress? older brother, Griffin. The True Grit actress didn?t exactly deny the rumors while speaking exclusively with Us Weekly last month.