I'm not sure if it has been mentioned yet, but could you possibly arrange for a therapist to ride with her on a few outings? The "exposure therapy" the doc recommends is very basic CBT, A highly proven method for ridding yourself of phobias. It is more powerful than any drug treatment for anxiety and fears. Just exposing yourself repeatedly CAN work, but it can also be stressful and without the right frame of mind, can make things worse. A few rides with a therapist (im sure they would be willing to hop in the car for some good old fashioned CBT) who can talk her through her thought process and teach her ways to cope would likely have some pretty miraculous results. No need to go it alone.
The swim/drown example really isn't the best one, lol. CBT and exposure works because the stress response people have can only be felt for so long, so if you "ride out" the stress response (which is very real and very strong) and see that nothing bad happened, the response lessens until it goes away. Generally it is done in stages. Ie, sitting behind the wheel, then driving slowly, then driving slowly alone with no one in the car, then on a moderately travelled street all the way up to highway etc. It totally does work, its a matter of biology and a little bit of dedication on the person's part. I have seen some very intense phobia's pretty much cured within a relatively short amount of time. Biggest key I think is having the person understand that they will feel the discomfort and it cannot be avoided. As soon as they feel it lessening, even when faced with their fear, it switches on lightbulbs for folks that thought previously that it couldn't POSSIBLY let up it was too strong.
