Share songs without duplicating music files.

Our music is in a shared network folder which is a disorganized mess. My laptop iTunes has all the songs well organized and I synch it to my 150gb iPod. My wife would only like a small portion of the songs on her smaller iPod, but since the shared music folder is disorganized, it's impossible to find the music she wants from there. When I drag songs from my iTunes to hers, the music file (m4a, mp3) is copied to her laptop or duplicated on the shared drive. How can I drag songs from my iTunes to hers without duplicating the music files? Basically, I'd like to drag just the "pointers" from my well-organized iTunes to hers so she can synch her iPod with only her selections. Thanks!