I can't speak to whether or not riding a tandem helps a non-rider to learn to ride solo, but I will say that my wife is in the exact same boat as your wife. She never learned to ride as a child. I tried to teach her several times using the "remove the pedals" method. I also had a "bike buddy," which is basically a inverted u-shaped bar that attaches to the rear hub. You run along behind the learner essentialy balancing for them, until they learn to do it for themselves. Both methods were unsuccessful. Last year, we rented a tandem, and were able to ride with no problems at all. We plan to purchase a tandem this summer. My hope is that she will naturally learn about balance and lose her fear of falling. Hopefully, by the end of summer, she will be riding both tandem and solo.