Hm. That's quite a different interpretation of Rowling's biography than mine, at least. I see a woman who tried to get a job, was unable to do so, and used the time while she was looking for work in a productive way, which ended up getting her a new job (as a full-time writer). I don't know how the welfare system is run in the UK, but where I live, you have to show regular evidence that you're still looking for work in order to get that check.
And, as donovanh points out, she's certainly paying taxes now-- far more than she ever took from the system, I would wager.