You are mixing up the rules.
Due to her age, there is no requirement that her parents provide more than 50% of her support, only that she did not provide more than 50% of her own support. She did live with them more than the half the year, so they likely can still claim her. See this:
https://apps.irs.gov/app/vita/content/globalmedia/teacher/worksheet_for_determining_support_4012.pdf
In any case, you cannot claim her since she (who is unrelated to you) didn't live with you all year.
