If it's a DRM-free book you can just download it from the website (while logged into your account, go here:
http://www.kobobooks.com/library/reading.html) and side-load it onto her Kobo (open the Kobo app, go to the library page and press the menu button to see the option for importing content). If the book offers a DRM-free download you'll see the option to download listed as "Download ePub" rather than "Download Adobe ePub".
Otherwise, there's no easy way of doing it without downloading the Adobe ePub and removing the DRM. Maybe try calling Kobo support?