I probably should have clarified better her capability.

It's not that she can't figure out how to use multiple apps, but it would be much easier for her I'm guessing if all her books are in one app instead of bouncing between 3 of them to know which has which. I know it only takes maybe 10 seconds max to get that answer by tapping all the apps, but just want to keep it simple if possible.
She actually said that she didn't like the kindle and was considering buying a NookColor at the local store. I just think for the money difference, getting the used iPad for only $40 more (net) is much more worth it. After testing the iPad I used to have, she likes that she can do e-mail easily on it, browse sites, watch videos, view photos of her grandkids, and listen to music as well.