How did she reveal the information of her past history? Is it in writing?
I’m not in the health insurance business, so I don’t know if the health contract might include any disclaimers for pre-existing conditions, even those disclosed.
Wait until the company gives the reasons in writing.
Even though it seems like your sister should be completely covered, it looks like it’s going to take an attorney writing a threatening letter at minimum. Chose someone who specializes in health insurance related issues.
Her application “interview” was 3 hours long and it was taped by Humana so they have her own words and declaration that it had been 3.5 years at least since she’d been to the doctor. She even asked them in the interview if she needed to go back beyond 5 years and they told her they would be looking at her health records so they would know her whole story.