A day after she checked herself out of Malibu’s Promises rehabilitation clinic, Lindsay Lohan was spotted partying at a Las Vegas nightclub.

According to reports, the starlet left Promises on Friday, after completing a 45-day program, her rep Leslie Sloane Zelnick confirmed the news.

"On Friday, July 13, 2007, Lindsay Lohan successfully completed her 45 days of residential and extended care treatment at Promises. She has transitioned to an intensive outpatient program, which includes attendance at daily AA meetings, outpatient therapy and daily testing," People magazine quoted Sloane, as saying.

Zelnick also said the "Mean Girls" actress spent her weekend in Vegas where she organized a surprise party for her roommate/assistant, Jenny, at Pure nightclub.

The 21-year-old starlet, who is set to continue her recovery outside rehab, is voluntarily wearing an alcohol-detecting ankle bracelet.

"On her own, she has also made the decision in support of her sobriety to wear an alcohol monitoring bracelet. In part she is wearing the bracelet so there are no questions about her sobriety if she chooses to go dancing or dining in a place where alcohol is served," Zelnik said, adding that when she spoke to Lindsay in Vegas, she'd opted to eat chocolate chip pancakes over going gambling.

Zelnick insisted that Lindsay is trying really hard to stay away from alcohol and so far she’s been successful.

"She's doing great. Lindsay is working hard on her sobriety and we are all supporting her," the rep added.

"Lindsay was totally sober all weekend in Vegas," one pal swears. "She's limiting her time with her old friends. Dori meets her needs perfectly - a sober girl who's more than happy to go wherever Lindsay wants, whenever Lindsay wants."