A source told ET that Steinfeld and Horan's fun continued into the night, as they headed to XS Nightclub in Wynn Las Vegas following the show. According to the source, they sat together at a stage table with a few friends while listening to a DJ set by Diplo.
Fans began speculating earlier this month, however, that Steinfeld and Horan broke up after the singer did not publicly wish her a happy birthday on Dec. 11. On top of that, Steinfeld was also spotted hanging out with her ex-boyfriend, Cameron Smoller, a month prior.
Though Steinfeld, 22, and Horan, 25, never officially confirmed their romance, the actress briefly spoke about what it was like to "fall in love" with someone special in the December issue of Cosmopolitan.
"When you fall in love, you pick up on the tiniest things about yourself," she said. "You start doing things for this person and going out of your way to make them happy. When you love who you are with that person… there's nothing that compares."