Possibly, depending on if she filled out her return properly.
With her income level being $4,500 (earned income) for the year, she could qualify for Earned Income Tax Credit. This is a credit that is also refundable. So if the credit brings your sister's taxes to zero, she could still get money, to the credit limit of $5,572 for two qualifying children. If the child not going to school is under 19, then that would bring the limit to $6,269.
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