Michigan and Indiana have a reciprocal agreement. Normally a MI resident would not pay tax to IN. However, the agreement only applies to full year residents. So, for 2022, she will need to file in all three states. MI will give her a credit for any tax she has to pay to IN. She must pay tax to her resident state (MI) even though the earned no income there. She pays MI tax only on the income received while a resident, regardless of where earned.
For future years, she will not need to file IN. Her employer should not withhold IN state tax.
As for IN county income tax, see https://ttlc.intuit.com/community/state-taxes/discussion/i-live-in-michigan-but-work-in-inidiana-why...
