Bumping this thread and asking if additional driver policy has changed over the years. From reviewing the links below I get the impression I need to stop by the counter and get my spouse to fill out a form so she can also drive the same rental car.
https://www.avis.com/en/help/usa-faqs/additional-driver
https://www.avis.com/content/dam/avi...8610026557.pdf
I tried to add it online to the reservation but it wants to charge me the extra driver fee.