Thanks for your question.
Here is how this will work.....it is a fairly common occurance.
1. The money is considered earned in the state in which work was performed. So, both states will lay claim to the taxing of earnings for work performed in their state.
2. For the state in which she is a resident..her permanent abode or domicile, she has to report her world wide income, regardless of where it was earned. That state will give credit for taxes paid to other jurisidictions, so she will not be double taxed according to what the definition of double taxed is.
She may owe additional taxes only because of the differences in how taxable income is derived and the difference in tax rates between the two states.
3. The state for which she was not a resident will require either a non-resident return or part year resident return.
A resident or part year resident return is required if a person both resided and worked in the state for 183 days or more.
You are welcom, and best of luck to you.