If her domicile (her main, primary home) is not in DC, and if she did not maintain an abode in DC for 183 days or more during the tax year, then she has no tax obligation to DC.
If DC taxes were incorrectly withheld from her pay, then she should file formD-40B in order to obtain a refund:
https://otr.cfo.dc.gov/publication/2024-d-40b
**Answers are correct to the best of my ability but do not constitute tax or legal advice.