Lindsay Lohan was seen drinking vodka on Thursday, it has been reported.The actress, who entered rehab earlier this year to be treated for alcoholism, partied in New York without lover Calum Best last week, and has reportedly worried friends by hitting the bottle again. A source told the New York Post newspaper: "Lindsay hit the Anchor Bar with two pals and was spotted drinking vodka straight from the bottle."After leaving the Anchor Bar, Lindsay, 20, headed to the Sway nightclub and danced for an hour before returning to Anchor.The 'Mean Girls' actress then hopped on a private jet and flew back to Los Angeles at 3am. Despite reports Calum - who is a renowned womaniser - has cheated on Lindsay several times since they began dating last month, the pair are said to still be very much an item. A source said: "Lindsay and Calum are still going strong."Lindsay's representative had no comment on claims the actress had been drinking vodka.