Hmmm, sounds like a situation for an electric vehicle of some sort. I'm not suggesting a new Chevy Volt-though once plug-in hybrids are available, it would fit the bill. I know that there are some planned communities that have zoned lanes for little electric vehicles (called GEMcars-made by Chrysler) that are like enclosed golf carts on steroids. Don't know if that would be street legal on this particular road. Also don't know what the Chrysler bankruptcy did to this company. Is this a freeway, major highway, county road with no shoulders? Is the problem heavy traffic, no shoulders, both, something else. Would an electric scooter be a possibility in good weather? Segway?
If you did go with an IC engine, there are some things like (again) golf carts, utility vehicles like Kawasaki Mule, Kubota RTV, JD Gator, or perhaps an ATV.
I know these sound like some pretty wild thoughts, but then again, it sounds like you are looking for something other than a traditional vehicle, so hope this might help.
Links to small electric vehicles:
http://gemcar.com/
Lakewood Ranch, Florida - An Award Winning Master Planned Community
Planned Community Goes Green With GEM Electric-Car Friendly Designation - Science News - redOrbit
This is another "out there" thought: if you put an engine block heater in the engine of a regular car, put it on a timer such that it comes on and pre-warms the block for a couple of hours before she leaves for work, that might decrease the amount of time it takes for the engine to fully heat up on this short drive. Again, I know this is sort of a wild outside the box idea, but just trying to think creatively.