My mom lives in Michigan, she moved from Illinois to Michigan and got a job in Indiana does she file all 3 states? How do you split the income?

My mom worked in Illinois and got an Illinois w-2, during the year she moved to Michigan and became a Michigan resident and got a new job; however the new job is in Indiana. The Indiana company sent her a w2 the w2 shows her Michigan home address, but the company's address is in Indiana. The company is located in Indiana. Does she file state returns in all 3 states or just 2? How does she split the income/deductions/etc?