Troubled actress Lindsay Lohan was joined by her mother and siblings as she turned 21 in rehab on Monday (27Jun07). The Mean Girls actress was charged with driving under the influence after smashing her car in Beverly Hills, California in May (07). She checked into rehab facility Promises shortly afterwards. To celebrate her landmark birthday, Lohan took a break from her stay at the clinic to host a party at Courteney Cox's residence in Malibu, California. She was joined by family and friends, including DJ Samantha Ronson, at the low-key bash. Lohan called off her original plans for a two-day birthday celebration at Pure nightclub in Las Vegas shortly after checking into rehab.