In the opening post it was mentioned:

I'm think of putting in a bench vice on her counter.

One type of jar opener that might be of some use is just a flat, usually plastic, device with a wedge shaped gap between two toothy jaws. You place it on the bottom of a counter top so that you can wedge the lid of a jar into the jaws and turn the jar.

Obviously, the jar needs to be right side up, so this device would need to be on the bottom of a counter or perhaps on the bottom of a cabinet (near the sink to clean up the inevitable drips?).

It's advertised as being an aid for removing "difficult lids" and for that purpose it doesn't work too well. If the lid is really stubborn it's difficult to hold the lid firmly enough against the jaws to keep it from slipping; but it might be okay for a one-handed person dealing with "ordinarily tight" lids.

I'm sure you'll recognize it if you find one, and it should be cheap enough to be a throwaway if it doesn't work (unless you buy it on late night TV).

John