So if you go into "Store", it looks like a web page? Or are you saying there's a web browser in the Kindle?
I've always sideloaded my ebooks on any of the various readers I've purchased, so I've never bothered to find out how the shopping menus work.
She won't be using Wifi because she doesn't have internet, for what that's worth. She bought a tablet 2-3 years ago with the plans to get internet set up and then just never did. She has no interest in driving the thing to the library or local Starbucks or McDonalds to search on Wifi. The only things on that tablet are things I've put there for her. Sigh.
That's why I really need idiot-proof instructions for her. She'll never use it otherwise. Makes me crazy, because she complains and complains about the STACKS of paperbooks in her home, and this would save her such frustration....if she'd just use it.