I suspect that the additional driver fee waiver for your acquaintance was done as a matter of courtesy, not as policy. This can be done, but isn't all that common.

The policy is that second driver fees are waived for Gold member spouses, domestic partners, and co-workers. Domestic partners is wide open to interpretation and lack of documentation; and even with spouses it isn't like they ask to see a marriage license.

Another possible option, though, is USAA. USAA waives the underage fee and I suspect would be a good leverage in waiving the additional driver fee, although for some reason the benefit is not specifically written as such.

This is the USAA benefit for additional drivers on Avis, Budget, and Enterprise:But this is the USAA benefit language specifically for Hertz, with my emphasis added:Either way, I heartily suggest you book your reservation as long as it is cancellable -- in the USA all reservations are cancellable except pre-paid. That way you lock in the advance rate. If the rates go down, you can always re-book.

And if you do go with USAA, perhaps Avis, Budget, or Enterprise will work for you. Those three waive the the underage driver fee (21-24 only, not 18-19) for USAA at Avis, Budget, and Enterprise, and the additional driver fee as well.