Since she lived/worked in Wisconsin and Illinois, she can file Part Year Resident returns for both of those states, declaring the income earned/tax paid there.
However, she also paid CA taxes, so can file a Non-Resident return there, (if she never lived in California in 2023), or file another Part-Year Resident return there if she did live there for a time.
Here's more info on filing a Part-Year Resident Return.
She can be a Part-Year Resident of several states, without being a Resident of any of them, although where you lived on December 31st can be considered your Resident State.
In that case she could elect Wisconsin as her Resident State, as you mentioned, and file Part-Year returns for the other states, although where you lived and worked the longest does not necessarily constitute residency.
Here's more about What is My State Residency Status?
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