It is odd, I can’t say I have ever heard of it either.
Here, for me, is a good case of someone needing health insurance. As a Nanny, her employers probably do not have a ‘Plan’ they pay for and depending on what she actually gets paid ... hope this working woman could afford it.
The father talking about the debt he owes the nanny should be paying her medical bills, or paying a whole bunch of them or making arrangements to do so.