Perhaps create an app or website that reads text. You paste in the text you want it to read to her---web pages, books, e-mail, whatever. Each item you "push" to her gets queued up so she can listen when it's convenient.

The controls she would need would be very simple. At a minimum, start reading and stop reading. Maybe something to skip to the next item if she gets bored with whatever she's on.

My mother is disabled, so I've thought a lot about these kinds of issues.