Madonna has been accused of acting like a "bitch" and snubbing director Ang Lee at an exclusive pre-Oscars party.The 'Hung Up' hitmaker reportedly stunned guests at the Creative Artists Agency (CAA) pre-Oscar reception at the Greystone Mansion in Beverly Hills last Friday (22.02.13) with her rude behaviour and bad mood.One onlooker said: "It was incredible - she stormed around as if a black cloud was following her and then she was gone. Everyone wanted to know what bug got up her arse."Another guest added: "She was just rude to most people she came into contact with. She really behaved like a bitch that night."The 54-year-old star is said to have particularly shocked people with her rudeness to filmmaker Ang Lee - who picked up the Best Director prize for 'Life of Pi' at the Academy Awards days later - snapping at him when he introduced himself and replying "I'm not interested" when he tried to instigate a conversation.When the filmmaker tried to speak to her again, Madonna turned her back and ignored him.Despite the reports from the party - where guests also included Bradley Cooper, P. Diddy, Jennifer Aniston and Leonardo DiCaprio - an associate of Madonna told the Daily Mail newspaper she was "in the best mood" but admitted reports of people thinking she is "a bitch" were "not unusual".The insider added: "It's not unusual that people might find her a bitch. She's not walking the room, smiling like Kelly Ripa. She's not a prom queen."She was not rude, though she could have potentially made someone feel that they shouldn't say hello to her, and that wasn't intentional, and perhaps some people might have thought she didn't seem approachable that night. And she didn't leave in a huff."She also denied that Madonna had been rude to Ang Lee and said she had invited the director to her own party on Oscar night.