She pays taxes, just not federal income tax. Sales, payroll, etc.
Low income people don't pay federal taxes by bipartisan design. From the tax policy center http://taxvox.taxpolicycenter.org/2010/04/15/about-those-47-percent-who-pay-%E2%80%9Cno-taxes-%E2%80%9D/
"There is, however, another reason why some people don’t pay. For decades, both Democratic and Republican governments have made conscious policy decisions to remove low-income working families from the income tax rolls. And, guess what, sometimes government policy works exactly as intended. That’s what happened this time.
Let’s take one of the biggest drivers: the Earned Income Tax Credit. Based on an idea (the negative income tax) originated by conservative icon Milton Friedman, the EITC is refundable, so that people who work for low wages can not only wipe out their income tax liability, they can even get a cash payment from the government. The EITC was enacted in 1975 under President Ford, greatly expanded in 1986 under President Reagan, and expanded again under presidents Clinton and Bush (both of them). It's been the very model of bipartisan tax policy (which, I suppose, is why some dislike it so). "