OP,
Pretty sure that what we have here is "a failure to communicate" - your wife is 72 has arthritis and is not small statured, you are trying to buy her what you think will work for her but that is not working out so well.
Let her try a 22 revolver - it is pull the trigger simple, keep pulling the trigger until it doesn't go bang anymore and then pull it a couple of more times. No recoil, intuitive and simple to operate - I don't know how this can be so hard.
drover