If she is filing a FAFSA for 2018-2019, she needs to report her dad’s income from 2016…from wherever he was living…on the FAFSA. She is a citizen…right?
http://www.marquette.edu/mucentral/financialaid/resources_non_filing_letter_instructions_1718.shtml
This is from Marquette University…but the process is the same for any college. Some schools (like Princeton) have their own form…so you could check your sister’s college.
When she did her FAFSA, did she include her dad’s income from 2016?