What puzzles me is the size of the Premium Tax Credit (PTC) that got repaid. I am having trouble understanding how she got that much in the first place.
Did she report a very low estimated income to the federal marketplace at the beginning of 2017? Did she have significant change events in 2017 (like getting married to you or making far more money that she expected) that she did not report to the marketplace in mid-year?
$19k is very expensive but not totally unbelievable, particularly for a nice (gold) policy.