https://uscode.house.gov/view.xhtml?req=granuleid:USC-prelim-title8-section1101&num=0&edition=prelim
“33) The term "residence" means the place of general abode; the place of general abode of a person means his principal, actual dwelling place in fact, without regard to intent.”
She in fact is not actually dwelling in IL for the past 3 months. Not even a day.
If she spent the majority her 3 months in IL, easy case: she has been an IL resident. If she even spent a plurality of her days in IL, easy case, still an IL resident.
Of course not. That isn’t the issue here.
The issue here is an LPR who does not live in the U.S. or IL who wants to naturalize.