Legal Question in Civil Litigation in Michigan

Yes, an oral contract is enforceable. The problem will be convincing the court that your version of the story is more accurate than her story. She will likely claim that no money is owed, so be prepared to show the value of the car (at all times relevant to the transaction) as well as your legal right to assign the lease to her. Hopefully, you have kept notes of dates and the content of your discussion and negotiations and agreement with her. It is not relevant that she is a co worker, but you should consider whether or not this contract dispute impacts your work or job.