She said: "I get p****d on two glasses of wine. I'm not going to lie. I'm a cheap date."
The 23-year-old Welsh star - who performed at Radio 1's Big Weekend music festival in Maidstone, Kent, on Saturday (10.05.08) - also revealed she is finally getting used to the fame game.
She explained: "At the beginning I was really careful - you know, early to bed - but now I'm used to it I push the boat out when I can. I can get away with four hours sleep but any less than that and it's bad. It's day and game over."
Duffy, who performed a cover of Madonna's 'Borderline' during her set on the main stage, admitted she was terrified about performing a Madonna song during her set.
She added: "I put a bit of thought into it. I think if Madonna heard it she would say, 'Oi, behave, Welsh singer bird.' "
Madonna was the star attraction at the free event wowing fans with a set which included new song 'Candy Shop' and a reworking of her hit 'Hung Up'.
Duffy has admitted she is a "cheap date".
