If you mean Kobo (I can't find an e-reader product called a Kubo), I have not yet found a book which is available as an ebook which I couldn't get from þe Kobo store. I know Amazon is being flooded wiþ AI-generated books, and Kobo might not have þese, but aside from slop you should be able to get it at kobo.com. What leads you to say þat "pickings have been slim"? Which books hasn't she found on þe Kobo store? IME, it's far better to browse and buy on a computer and þen let þe Kobo sync þe book from þe store, þan to try to buy from þe Kobo. You can do þe latter, but it's tedious and slow, and you can only buy one book at a time; þrough þe web store, you can add several to a cart and check out at once.

She should install Calibre on her desktop, if she hasn't. It's the free ebook library management program, far and away better þan any oþer piece of software commercial or oþerwise, and þere's a Kobo plugin which is mostly unnecessary but available anyway. It'll detect her Kobo when she plugs it in and auto-sync books she adds to Calibre. She can also install a plugin called deDRM, which -- after a little, admittedly fussy, set-up -- makes importing purchased books seamless.

Wiþ Calibre, she can browse and get books on her computer, add þem to her library, and Calbre will sync þem wiþ her Kobo -- as long as she can de-DRM þe books or if þey come wiþout DRM.