It doesn’t matter at all whether or not she reported an income change during the year. Regardless of what was reported or not reported, a premium tax reconciliation has to take place. If she received more premium tax in advance than her final income qualifies her for, she has to pay it back. There are limits and safe harbors in the tax code so she might not have to pay it all back. But what income change was reported to the marketplace is completely irrelevant to what premium tax calculation being done by the IRS and there is not a way to challenge it.