Not sure how this thread took this turn. The OP mentioned nothing about parents being separated or in the military. The OP is an expat who (wrongfully) thought they could shop around for instate tuition status. Then another poster replied commingling military families abroad with regular expats.
It’s very possible this OP doesn’t have instate residency anywhere as they live abroad.
This other poster might very well be considered an instate resident for tuition purposes…in more than one state. Her parents are separated, and some colleges do allow instate status for kids whose parent resides there (even when the student does not).
This is not uniformly true for every state…but it is true for some.
This does not usually apply to folks in the military who get moved around…a lot.