Britney Frolics with Dancer-Family Man

04/28/2004 at 01:00 AM EDT

Britney Spears, homewrecker? That's the word from former Moesha costar Shar Jackson, who claims the pop princess stole her boyfriend of four years, dancer Kevin Federline, PEOPLE reports in its latest issue, on newsstands Friday.

"It wasn't like just breaking up a relationship," says Jackson, 27, who has a 21-month old daughter and is also seven months pregnant. "It was like breaking up a family."

Spears, 22, met Federline, 26, shortly before she left on her European tour, which kicked off Monday in London. The singer spent a few days in Los Angeles, where she went dancing at the hotspot XES on April 22, then continued on with friends to El Centro past the club's 2 a.m. closing.

"She didn't seem to have a care in the world," says an onlooker.

The next day she and Federline – once a dancer for Justin Timberlake – left the Beverly Hills Hotel in her white Mercedes and drove to the beach in Santa Monica, (stopping for Subway sandwiches en route) where they strolled in the sand and posed for paparazzi.

The two returned to the hotel and did not emerge until the next afternoon.

"I know Britney in passing. We've run into each other at a couple of events," says Jackson. "She knows who I am, she knows I'm his girlfriend."

But a source close to Spears denies there's a romance between she and Federline, saying, as reported by PEOPLE: "Britney's just having fun."