Setup a Calibre-Web server (
https://github.com/janeczku/calibre-web). Runs on top of a Calibre database and offers Kobo sync. Basically you change the Kobo store URL to the location of your Calibre-Web server and then when you sync the Kobo it syncs with your "store". You can set it up so that only certain shelves will sync and it can still sync to the real Kobo store if you or her do purchases there. I've been using it on my Libra Color and it's great. Only complaints are it doesn't sync reading progress, just the books nor does it do PDFs just ePub. Might be overkill for your purposes but for me, it's been the best way to manage my eBooks I've ever had.