Stephanie Pratt Stephanie Pratt

The Hills' Stephanie Pratt pleaded not guilty to a misdemeanor DUI Friday and plans to enter a 30-day residential rehab facility, People reports.

Pratt, 23, was arrested in Hollywood the morning of Oct. 18 for suspicion of a DUI. She was released the next morning on $5,000 bail.

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She faces up to six months behind bars and a $1,000 fine.