If she doesn't get that thing out on the freeway once in a while to get it good and hot, and keep it at running temp for at least 20/30 miles your gonna have more than rotting exhaust system parts. Gummed up valves, carbon buildup in the heads and cylinders, generally crud buildup in the engine result from never running an engine long enough, to get it hot enough to burn off all the nasty corrosive chemicals created by the combustion process. Do yourself a favor, save a few bucks to spend on a couple gallons of gas to run that rig on the freeway for awhile once each month. In the long run you'll be saving big $ in repairs to your engine.
Better yet, Have your wife ride a bicycle the 2 miles to work. She'll really save money then.