You have to fill it out as self employment income and answer the business questions for her being the business. She is filing schedule C. Self Employment means she does have her own "business" for it.
You should ask the employer why they gave her a 1099NEC instead of a W2. How long did she work there? You or she didn't notice they were not taking any federal or state tax withholding out or FICA SS & Medicare taxes? You can file form SS-8 if they should have paid her as a W2 employee but I don't know how that works.
https://www.irs.gov/pub/irs-pdf/fss8.pdf
