Truthfully, any eReader will likely be good for such a situation. With books, they are either in a format with large type or they aren't. With an eReader it is easy to adjust the font size and style to one that you are comfortable with. It was a good question though and it merited some research. I wanted to advise her well and with more than a generic suggestion.
In my search I found this site which I think substantiates the user's explanation thoughtfully. And so, Barnes and Noble's NOOK products come out just ahead of Kindle.
http://tinyurl.com/PCWorldOnEReaderResolution (Click at the top right of the page to skip the ad)
"Trade books, mass-market books, textbooks, magazines, newspapers, and children's books all look and function better on the Nook Tablet than on the Kindle Fire.
Both tablet's screens have a resolution of 1024 by 600 pixels, which limits how sharp the text they display can be. But the Nook Tablet's screen is less reflective than Kindle Fire's; the LCD is bonded to the glass, which mitigates reflection and increases contrast and sharpness. In comparison, I often encountered glare on the Kindle Fire's display.
I looked at the same magazines and books on each device, and the Nook Tablet was the clear overall winner at rendering text. At comparable font sizes, text on the Nook Tablet looked crisper than on the Kindle Fire.
In presenting standard books, the Nook Tablet offered more meaningful viewing choices. Though both tablets provide eight font-size options, the sizes on the Nook are more useful. It's definitely better for readers who need large type."