Stephanie Pratt heads for 30-day rehab

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updated 9:09 p.m. ET Nov. 15, 2009

Stephanie Pratt pleaded not guilty to misdemeanor DUI in a Los Angeles court Friday and will enroll in a 30-day residential rehab facility.

The “Hills” star, 23, was arrested last month in Hollywood after driving home from Holly Montag's birthday party.

She recently told PEOPLE that the arrest "was the worst thing to happen to me and, at the same time, it was the biggest blessing" as a life lesson.

If convicted, Pratt faces up to six months in jail and a $1,000 fine.