The IRS already knows!The IRS will find out eventually.
They just have not acted, yet.
The penalty for late payment is 1/2% (1/4% for months covered by an installment agreement) of the tax due for each month or part of a month your payment is late.
The penalty increases to 1% per month if the IRS sends a notice of intent to levy, and you don't pay the tax due within 10 days from the date of the notice.
Since she only made ~$8,000 the taxes may be low and a payment plan may be offered.