Richie was accused of driving while drinking in December in Los Angeles.
The star was not in court to make her plea, and may need to do 90 days in prison.
According to the authorities, the 25-year-old was seen driving her vehicle on the wrong side of the road on December 11.
The police have confirmed that the star admitted consuming marijuana, and a painkiller, Vicodin. She had to pay a fine of $15 000.