I suspect that she received some form of living allowance and that must be the significant amount reported on your daughters W-2.
Per the Americorps website, "your daughter would be responsible for any income taxes owed on any AmeriCorps living allowances that they receive. The living allowance amount received in a calendar year is subject to income taxes for that calendar year."
Thus, in my opinion it is very possible that your daughter may not have had adequate withholding of federal income taxes. Hence, she owes a potential $1,000 in federal income taxes for 2009! But, I am curious as to how much was reported on her W-2 for 2009?