I still struggle with organization and a lot of how you describe Sarah is familiar to me. Anyhow, two things that are working for me are: (1) using multiple colored half-cut (?) folders for filing - the kind where you slide papers in but can still see the top half of the sheet. They are very similar to file folders, but bc I can see what's in them, it just makes putting things away/organizing easier - you could get a few of each color to coordinate with the various subjects and she could slip the papers into the appropriate colored "folder" and keep them neatly stacked on her desk to put neatly away later. Notice that I didn't say "file", filing doesn't work for me - stacking/piling does. And (2) using a flat filing system - where things get stacked flat into seperate flie slots.
I'm on blackberry now, so I'll try to post pics or links later to explain better.