When we first listened, the inestimable STB opined that she was unlikely to be able to do it like a dude, or for that matter, do it like any gender, without benefit of Auto Tune. This certainly seems to be the case with the single, but there's a video of an 'acoustic' version here, which shows that apart from not being able to say "motherfucker" without wilting, she's actually pretty good at teh chanteys.
Not that I had my fingers crossed that it would be the British Christmas Number One. I had my hopes pinned on Cage Against the Machine's 4'33" for that - a complex joke involving trying to keep X-Factor winners off the Christmas number one spot (last successfully attempted by Rage Against the Machine) by re-recording John Cage's famous composition 4'33", four minutes and thirty three seconds of incidental sounds as the musician sits in front of his instrument and the audience waits. (Most often described as four minutes and thirty three seconds of silence - it's not; the instruments are silent, but not the performance.) Alas, CATM lost out to X-Factor this Christmas, so I will play Jessie J instead - or perhaps just have a few moments of silence with CATM.