I always, always duplicate a copy of whatever I'm working on onto one of those little memory-stick drives that slot into a USB port. Put a shortcut-icon for it on the desktop (on the Mac you get a disc-drive icon the minute you insert it) and just drag your Word-file into it, which will automatically copy itself and replace the previous versions - you can rename or number them if you want to keep the old ones too. You don't have to close the document (just minimise it if you're using your whole screen) though I expect it will only clone the most recent saved version. That way you have a back-up copy that is completely independent of your hard drive.

Incidentally, she might think about saving more often - it's easy enough to hit either Control-S or Command-S frequently. It's become a reflex with me now.