What you describe, there for an internship, is a temporary absence form you home state of MN. You should do as the original answer said: file a non resident IL return, reporting your IL income. Then prepare a MN resident return, reporting all your income and claim a credit for the tax paid to IL. Prepare the IL return first.
You could make a case for filing as part year resident of both states, depending on the nature of your time in IL. But, TurboTax doesn't handle rotating residency very well and the tax , almost always, comes out the same either way.
