GLENDALE, Calif. – Nicole Richie pleaded guilty Friday to driving under the influence of drugs and was sentenced to about four days in jail and fined by a court commissioner who said she was lucky nobody was killed when she drove the wrong way on a freeway.

Richie, the 25-year-old daughter of pop singer Lionel Richie, was subdued and somber as she was lectured about her driving. She entered court on the arm of boyfriend Joel Madden.

Richie, who’s rumored to be pregnant but has not confirmed it, stood before the judge and softly answered “guilty” when asked how she pleaded to the misdemeanor charge. She initially pleaded not guilty in February.

She nodded when asked if she understood terms of the plea agreement (including 90 hours in jail and a fine of $2,048) worked out between her lawyers and prosecutors. Superior Court Commissioner Steven Lubell also gave Richie three years of probation and warned that she would go to county jail for a year if she violates it.

She must complete her sentence by Sept. 28. She can serve it in either a city or a county jail.

She was ordered to enroll in a drug and alcohol program and must prove that she has completed it when she returns to court on Feb. 20, 2008.

“You are not to drive with any measurable amount of alcohol or drugs in your system,” Lubell told her. “You are not to drive without a driver’s license.”

He said the state Department of Motor Vehicles would decide whether to suspend her license.

“You are very lucky that no one was hurt of killed as the result of this incident,” Lubell said.

Richie was arrested early on Dec. 11 after witnesses reported seeing her black Mercedes-Benz sport utility vehicle headed the wrong way on a freeway in Burbank.