What I would do in this situation is get her CDs MP3'd and then set up a custom playlist for her arranged like a stack of 6 CDs. I don't know anything about the unit's menu of playlists, but surely this is not much harder than using the CD head unit and stacker controls anyway? And you can tell her that this way she gets to choose the CDs by name (what's in slot #6 again?), she doesn't have to put up with skips and pauses (no CD changer is perfect), and once she's doing the MP3 thang she can have more than just six pissy little CDs to listen to... Then you sell the head unit and changer, and buy her some more CDs if she's still feeling unhappy.

Go, my son, and proselytise!

Save the whales. Feed the hungry. Free the mallocs.