Yeah, that was my original plan to upgrade the Acadia with the towing package but went to the dealer and asked about it and they showed me a recent release from GM stating that if the Acadia was not built from the factory with the towing package you can't increase the towing capacity. You can only just add a hitch. So her vehicle is stuck with the 2,000 lb towing capacity.
Scanning the internet now for used 197 or 228 for sale. These are both under 4,000 lbs.