She has to file because tax will be accessed. Her standard deduction is $3000 + 450 = 3450. 3879 -3450 = $429 taxable income = $43 tax. The "kiddie tax" does not apply, because of the low amount, but form 8615 must be filed.
https://www.irs.gov/pub/irs-pdf/f8615.pdf (see line 3).
