The star was caught on video yelling at a security officer during one of her three sold-out shows in Philadelphia over the weekend.
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Despite the incredible energy from her fans, Swift herself interrupted her performance.
Video shows Swift having "bad blood" with security. She could be heard in the video saying to security, "Hey, stop! She wasn't doing anything."
Swift was also seen shooing security away from the scene.
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Some fans originally said people were being pushed, and it appeared like someone was trying to climb on stage. However, that was not the case.
Concert-goers say security was very strict about keeping aisles clear during the show.
Superfan Kelly Kelly was in the front enjoying the concert and as Swift sang, Kelly danced -- but she said the security guard wasn't having it.
"He kept telling me to, like, calm down and, like, not to dance," Kelly said on "Good Morning America." "And I guess she noticed and she yelled at him and told her to leave me alone and that I wasn't doing anything wrong."
Other concert-goers said the security guard had no idea what was going on.
"So I was like, 'Hey, Taylor's talking to you,' And then he quickly, like, I don't know, he disappeared. He left," Kirstin Birmingham said.
Kelly is a third-grade teacher, a mom and a Swifty who camped out for a summer concert in 2014.
She said it was a glorious moment to see Swift sticking up for her fans.
"I think it meant so much to everybody else too, like her fans know that she has our back," Kelly said.
Kelly went to Sunday night's show where she had another chance to shake it off.