Another concertgoer also caught the "Blank Space" singer dancing with pop trio Haim during JT's show. The sisters and Swift were celebrating Alana Haim's 23rd birthday. "Happy birthday @babyhaim!" Swift tweeted. "So happy I got to watch you blow out your candles while you were singing a scandalous/perfect rap song. As you do."
This past October, Swift chatted with ET about her famous friends, disclosing what quality she finds most important in a gal pal. "A good girlfriend for me is someone who is an individual and has something that they are deeply passionate about," she said. Check out the video for more of our interview with the 1989 pop star.