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"She was rocking out the whole time," says one concertgoer. "She only seemed to know the words to his older songs though, because she sang along to 'Your Body is a Wonderland' and his older hits."
With a camera in hand, Simpson – who took in the show from the sound and lighting area alongside stylist Ken Paves, Billy Joel and his wife, Katie Lee Joel – snapped photos of herself and Paves, Mayer and the crowd.
"She was dancing like she was a real fan, and a lot of the crowd had their eyes on her the whole time," says the observer.
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