She didn't have a career before SCD.
The song isn't that great and nor is her singing in it. That's probably why it's done badly in the charts.
That said, I haven't liked any of her music. I loved Alesha as a contestant and was willing her to do well musically but 'The Boy Does Nothing' has the most moronic lyrics of any song I can recall. The other one, which thankfully I can't remember, wasn't much better.
I dunno though... maybe people who DID like her music have gone off her lately because of the judging fiasco. I certainly did within 3 weeks of her joining the panel. Where once she was down-to-earth and excitable and very unstarry, she now seems haughty and arrogant. She's not been the 'voice of the viewer' or the 'one who can empathise with the celebs' as the BBC intended; she's tried to sound like an expert instead.
And the Beeb's stubborn refusal to accept her limitations, like giving her a massive profile on Children in Need, puts me off her even more.