Jessica Simpson

Jessica Simpson Rocks Out at John Mayer Concert

By Jon Warech and Stephen M. Silverman

01/29/2007 at 08:00 AM EST

Jessica Simpson and John Mayer continued to share quality time together Friday night at his concert at the Bank United Center at the University of Miami, where Simpson was dancing to Mayer's entire set and 20-minute encore, sources tell PEOPLE.

"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.

Simpson, 26, and Mayer, 29, longtime friends who've been linked off and on since the summer, spent a lot of time as a couple in Miami last week, working out and dining together last Monday, then spending Tuesday heading toward his concert in Jacksonville.

This Monday, after an Orlando gig on Saturday, Mayer is due to perform in Pensacola.