The Mobipocket desktop software used to automatically synchronize to the Cybook is currently Windows only but she can definitely download from Fictionwise and copy the book to the Cybook like a disk drive. I'm sure that you could show her the process.
I just thought I'd mention that some people find the page button stiff. Worst case if she has a problem with it I'm sure you could sell it used. I would recommend trying it. I know I wouldn't want to be denied my books.