She is not required to file a MN return if her MN gross income is below MN's filing threshold, but she should file one anyway if MN taxes were withheld from her pay. See this:
https://www.revenue.state.mn.us/who-must-file-income-tax-return
If she chooses not to file, this TT help reference explains how to delete a state return:
How do I delete my state return in TurboTax Online... (intuit.com)
Her resident state of WI can tax ALL her income, including that earned in MN.
**Answers are correct to the best of my ability but do not constitute tax or legal advice.
