Man, if she is "elderly" at 60, then I must be decrepit at 66yo!
How about a 3 wheeler recumbent bicycle. You don't really describe her capabilities, but a 3 wheeler (a good quality, not a big clunker) is pretty sexy and exciting. If you want more info, check out the recumbent forum:
http://www.bikeforums.net/forumdisplay.php?f=37
It should give good support.
Also, a weight reduction program would be important, as would a strength program lifting weights, etc.
What does the doc say?
My wife also had a couple of car accidents. Through good physical therapy and a lot of bicycling, etc., she has made good improvement.
There are group cycling rides which should provide a nice social element.
Please tell us some more.