My wife is a manager for a restaurant in Michigan. A Chain restaurant. Recently, she has been reassigned to open a new store. She is always scheduled to work 10 hours a day, at least 5 days a week. When she is scheduled a 6th day, she is always paid for that day. With opening this new restaurant, she has been told that she will be scheduled 6 days a week, 10 hours a day, but will not be compensated for the 6th day, while everyone else in this company, excluding the managers opening this new restaurant (mostly doing the hiring/admin work). My question is: What are her options? Is she entitled to be compensated for this 6th day? Remember, she is a salaried employee.

Under federal labor law (FLSA), exempt salaried employees have no inherent legal expectation to additional compensation for hours worked past 40 in the workweek. That is what the word "exempt" means. There is no labor law problem per se with what you describe.

Now not all law is labor law. The employee maybe could argue that there is some type of implied contract, although that strikes me as a very up hill sort of argument. The "law of the land" is something called Employment At Will. There is a principal under that common law that absent a contract to the contrary, or some sort of legal exception, that conditions of employment can be changed on a go forward basis. The only obvious exception I can see is arguing that there is a valid contract acting as an impediment. While not all contracts are express (formally in writing), it is certainly vastly easier to take a written contract to court.