Hey Guys,
I'm with a lot of what has been stated so far. That original link that Nana put up, regarding the blind and visually impaired contained a post from my brother, who is very almost totally visually blind. He drips as he uses the Silver Bullet at 6volts, although most of the time it is a total pain for him. He ends up with juice all over him, and not in the atty.
That said, I think a longer lasting battery, such as in the wetbox utilizing the 14500, or the Ego would be the best bet, using a cartomizer. I know a few seniors who are blind, and who smoke, as my mom lives in a senior community now, and and boy they smoked a lot, so I imagine that she would vape a lot too. A longer battery life is the way to go. The standard 510's don't last worth a hoot, but the aforementioned batteries will last most of the day. Getting back ups (batteries), and having someone to help her charge them should do the trick.
As far as atty's go, I think the cartomizers might work best. I have yet to try the 510 carto's, but I started out vaping on the KR808d's and they worked well, and if the 510 carto's are as good as the reviews and talk of em, I think they should suffice.
Summing it up, I think the wetbox, or Ego with 510 carto's sounds like the ticket.