Britney Spears had good reason to be nervous about appearing in Madonna's Sticky & Sweet concert at LA's Dodger Stadium last night. After all, the other special guest star was none other than her ex Justin Timberlake.

But Brit didn't let Justin's presence faze her. "She arrived at the stadium on time, with her hair and makeup done," a Spears family insider tells Life & Style. "She even chose her outfit herself."

Brit's big moment came during "Human Nature," Madonna's third song of the night. The crowd went wild as Britney strutted onstage. "It was like Caesar returning to Rome," Madonna fan Joseph Toth tells Life & Style. "The light was back in Britney's eyes."

Brit and Justin did run into each other -- but only at rehearsals. "They passed each other behind the stage," the insider says. "Justin said hello, and Brit said hello back. It was small talk, nothing more. For the show, they were in well-separated backstage areas, and Britney left shortly after her performance."

Photo Credit: INF PHOTO; WIREIMAGE