Her 21st birthday party plans at Pure in Las Vegas have finally been scrapped, and it doesn't look like Lindsay Lohan will be replacing them with any sort of rowdy celebration — because she may still be in rehab. According to the New York Post, Lindsay may be extending the usual monthlong treatment at Promises rehabilitation center in Malibu. "She is staying in Promises longer than a month," reveals a friend. "We don't know how much longer because of her work schedule, but she is taking rehab very seriously this time and not messing around." Good for you, Linds!