My 24 year old child is away from ny state going to law school in vermont but her mailing address is still in ny state, how do i file her residency

[MinhT1]

If your daughter intends to return home after college, her tax residence is still in NY state as the IRS considers absences for attending college as temporary absences.

See this IRS document.

[TomD8]

Be aware that if she works in the state of Vermont, then at year's end she'll have to file state tax returns for both VT and NY.  VT can tax her as a non-resident on income earned in VT; NY can tax her as a resident on ALL her income, including that from VT.  In this situation she'd be credited by NY for the taxes paid to VT, so she wouldn't be double-taxed.