Schools determine who can get in state residency for admissions and tuition. Not FAFSA dependency rules, not IRS dependent rules, not divorce decree rules, not even State rules for voting, library card, drivers license, taxation, etc. Two different state schools can define residency different ways. It’s up to the school.
The rules for in state residency for Tuition can even conflict with that for state financial aid and scholarship and National Merit status.
That’s why, each student, parent, person has to check at each school. As general rule, a student has in state residency for tuition if a parent has been living there for a year. (Some don’t even care if it’s a year). It’s supposed to be the primary residence for the parent.
It gets even trickier because checking up and enforcement of these rules can vary widely
I know a number of military and a number of divorced parents whose kids can get in state tuition at more than one state.