Britney is "still shocked"

Things are even more hectic than usual for Britney Spears. On Thursday, after spending a cozy afternoon at her Beverly Hills home with sons Preston, 2, and Jayden, 1, the singer scheduled – then canceled – a session at Millennium Dance Complex. "She wanted to try out a new dance routine," says a source. But, in the wake of her 16-year-old sister's surprise pregnancy announcement, the studio was swarmed by hoards of photographers. When Spears, 26 – who had been kept in the dark about the baby news until the story broke on Tuesday – saw the crowd, "she freaked out and just kept driving," says the source, who was on the scene. "Britney said that she doesn't want to deal with the media because she is still shocked [about Jamie Lynn's pregnancy news]," adds the source. "She feels that she needs peace and quiet." Spears, however, was friendly with the photogs during a shopping trip with her assistant. The duo stopped by Carl's Junior, and, although Hollywood offers plenty of great shops, Spears hit a souvenir store where she picked up (and posed with) a Tinkerbell t-shirt and a pink bedazzled onesie.