Think about a Kobo, rather than a Kindle. They use a different format which means they can get books from Public Libraries as well as buying them. Some Kindles can use Public Libraries, the Kindle Fire series but they are tablet computers rather than just book readers and have quite a short battery life (hours, rather than days). You need the internet for either but you can download the books for her and then take your laptop to her house to transfer them. Library books do not need to be returned - they just expire after the loan period. You can also join more than one library without living in the area in some cases.