I can't remember exactly how this works, but I think that some percent of what you pay in child care, subject to a maximum, is available as a tax credit (gets subtracted from her tax liability). I think the write-off % or the maximum is a function of income level also. Sorry, I'm not much help, am I?
If she did her '06 taxes with TurboTax or some other program, maybe plug the numbers in and see what she would have saved and go from there.
cj/