The 22-year-old 'Heart Wants What It Wants' hitmaker shocked everyone at Swift's party with her outburst, reported Us magazine.
"She shouted, 'No one understands me! My boyfriend doesn't even understand me," a source said.
Her outburst reportedly left other guests at the star-studded party shocked. "Everyone just stared," the source added.
Just a week ago, Gomez said on a radio interview that she didn't date anyone. When asked about her on-and-off boyfriend Bieber, she said, "I definitely have so much respect and love for him."
"Going in the studio is just very therapeutic. It was my way of having it be a message more to people in general. People everywhere feel this feeling, and they should understand when anybody goes through that. They just can't help what they want and who they love."