I can't believe I'm doing this, but I'm going to defend Whitmer on this one. The American Rescue Plan forbids state reimbursement for tax cuts of any kind, so she is correct on the reimbursement being prohibited. This is a one-time expense, so the state will need to mimic the process and make direct cash payments. You can thank congressional Democrats for this restriction.
The other option would be suing the federal government for the unconstitutional restriction, but Dana Nessel is too much of a partisan hack. It's clear we won't see action from her on this one.