I would try out the black basic kindle over a tablet. If her sight is so bad, she may need something very very basic, so she does not end up in some settings menu and does not know how to get out.
I'd put a red or white dot on the home button, so she knows how to get to the home screen, and only maybe load one to three books at a time. The largest font is quite large, so try it and send it back of it's not working for her, since you have 30 days.
The black basic kindle has the best contrast I have seen in any eink reader so far!
My almost 80 yo aunt is current, reading on one of our old basic kindles, and she "got it" after some trepidation and set the font so large that she can read without reading glasses now.
Last edited by xendula; 12-21-2012 at 10:08 AM.