02/24/2008 at 12:00 PM EST
After a three-hour visit with her sons
on Saturday (her first since Jan. 3
), Britney Spears
continued her family time Saturday night, stepping out to Mastro's Steakhouse in Beverly Hills with her father, Jamie.
Just before 8 p.m., the pop star and her dad were joined by an assistant, a family friend and two bodyguards for dinner. Clad in a purple silk dress, Spears smiled and appeared in good spirits as she headed inside.
"Britney looked stunning and everyone turned around to get a glimpse of her," says a witness at the restaurant, adding that the group lead Spears to a private dining room. "Everyone seemed extremely protective of Britney."
The party of six dined on a seafood tower with lobster, steak, french fries and lobster mashed potatoes. But Spears's good mood seemed to diminish over dinner. According to an observer, "She seemed quiet." After numerous bathroom and cigarette breaks, Spears and co. left the restaurant around 9:30 p.m., making their way through a pack of photographers with the help of restaurant staff.
Asked if he'd ever helped a celebrity exit the restaurant, a chef told PEOPLE, "Never! It was like being in a war zone. I almost lost my [chef's] hat."– Reporting by PERNILLA CEDENHEIM