If this student is considered independent…then you are correct…the FAFSA would,be the way to go.
BUT if the student is not considered independent…and the sister is not a guardian…then the father would be the custodial parent for FAFSA purposes…because he is the only loving parent the student has. Doesn’t matter that she lives elsewhere.
Having said all of that…to the OP…do you have documentation of the abuse issues…a child protective services complaint, a police report, something in your school record? Of so, you might be eligible for,a dependency overrode by the financial aid officers at your schools. You would need to apply for this dependent override to each school…but with the documentation, it is very possible you would be deemed indeomednt for financial aid purposes.
If you are doing a Profile now, it sounds like you are applying early someplace. Contact that School and ask the, what to do to get a dependency override. Explain your situation, and be prepared to document it. They should be able to tell you what to do.