As we reported last week, Britney's been getting mighty cozy with one of the backup dancers on her tour -- but Gatecrasher says the fling was short-lived. In fact, Britney only made her move after Jamie left the tour to tend to some business in LA and it was over the minute he returned! Talk about a quick-step!

“Britney was a bad girl,” says a source. “Literally as soon as her dad left, she started getting cozy with a dancer named Gio. It wasn’t serious. They had a few romantic interludes, and she bought him a few things — a pair of shoes and some clothes — even though she’s on an allowance.” Spending her allowance on a boy? How middle school of her!

“Britney was definitely getting jiggy there for a hot minute, but they’ve slowed down since Jamie got back in the picture,” the source told the paper. “It’s basically over now.”

Guess he's no K-Fed 2.0!