Glad to hear your Gran has taken to it.
As an alternative for other people thinking about giving older people a knife, how about a CASE Mini Copperlock? I lent mine to a gent who is getting on and has stiff fingers,he opened it very easily as you can pinch it open&it has a long nail nick.The good part is it has a weakish spring being a lock back and closing it requires very little pressure or dexterity.It's also a slim but quite long compact knife that is non too heavy either,goog ergonomics too due to its Copperhead shape(difficult to slip through hands etc)
Spyderco is a very decent option,but some of them can snap shut very quickly if you are not yet familiar with handling them. The BM mini Grip is one of my faves but an axis lock could be tricky I think if you're getting on6not knife familiar.
One more suggestion.Böker Germany do a wonderful pocket lockback in Stag, you pinch it open and it has a small puukko style blade,easy to grip and shut,stubby and fat.