Stephanie Pratt Partied With Holly Montag Before Her DUI Arrest

Stephanie Pratt got her party started early Saturday night.  She celebrated Holly Montag's birthday along with fellow Hills star Stacie Hall at Empire Hollywood nightclub.

Stephanie was arrested on suspicion of DUI at 3:45 AM Sunday. She was handcuffed and taken to the LAPD Hollywood Division. She was released on $5,000 bail at approximately 10 AM.

Stephanie Pratt Arrested For Drunk Driving

Pratt is the sister of Hills star Spencer Pratt.  Birthday girl Holly - she turned 26 on October 15 -- is the sister of Heidi Montag who married Spencer earlier this year in a wedding shot for The Hills.

In June, Holly joined I'm A Celebrity...Get Me Out Of Here after her sister and brother-in-law left the reality show.

Holly Montag Thinks She Is A Celebrity.