That would be the result of the W-4 she filled out with the employer; she did not have enough tax withheld. Going forward, she can complete a new W-4 and have more tax withheld to avoid having to pay tax when you file your return.
https://ttlc.intuit.com/community/tax-topics/help/what-to-know-about-the-new-2020-irs-form-w-4-emplo...
https://www.irs.gov/pub/irs-pdf/fw4.pdfhttps://turbotax.intuit.com/corp/guarantees/
**Disclaimer: Every effort has been made to offer the most correct information possible. The poster disclaims any legal responsibility for the accuracy of the information that is contained in this post.**
