Q. I can't figure out how to tell TurboTax she didn't live in Kansas from mid-May to mid-August?
A. You don't tell TT that. It's not relevant. She was never a WA resident. She was only temporarily away from her home state of KS.
You report all your income on your resident state return, including the income earned in the other state. Your home state calculates tax on all your income, but gives you a credit, or partial credit, for tax you paid to the other state, if any.
When you worked in a state without an income tax (e.g. Washington), there will be no credit, since there was no WA tax. In other words, having worked in a state without an income tax does not get you out of paying state tax on that income, to your home state.
"She said the company said she should file as a non-resident for those two months". That means non-resident of WA. Since WA doesn't have an income tax, the statement is irrelevant.
