Britney Spears's deposition was an emotionally difficult experience , PEOPLE reports.

"We are going over things that are very, very gut-wrenching," Kevin Federline's laywer said Monday night.

"It's not something anyone would enjoy," he says.

"She was about 50 minutes late," he says. "After an hour I would have been over it. I was prepared to terminate had she not showed at that time."

Spears was spotted biting her fingernails when arriving to Kaplan's Century City Plaza office. After spending more than two hours there, Spears appeared tense and lit up a cigarette behind the wheel of her Mercedes before driving through Beverly Hills listening to Madonna on the stereo.