She can download them to her PC via Amazon then once they're on her PC plug the kindle in via USB open the Kindle then go into the folder I think it's books and just drag and drop the book into the folder Nice and simple.
Can you do this? My Aunt has bought herself a basic Kindle but she doesn't have wifi. You had to register it via a wifi connection, so I brought it home to do that, however will I need to do that for every book she wants or is there a way to transfer it once purchased by USB? I had a quick look through the user guide but couldn't see anything.