Kind of makes one long for the old days of film....
My gf isn't much of a photographer, but has had her moments of documenting things that meant the world to her. Some years ago I gave her a little Konica p&s (35mm) and it's served her well since then, and the negatives are always put away. I gave her a little Sony digicam this Christmas, and I'm hoping that the digital files don't wind up going astray for her. She doesn't deal with technical things too well, she's just not interested, and somewhere along the way (memorystick, card reader, photo editing software, archival storage, hard drives, Windows laptop, proprietary battery, digital photo terminology (mpixels, white balance, etc,) video, getting prints...
all that stuff is now different, and despite how easy it all
can be, it can also trip up someone who just isn't into it, other than taking pictures. Can we say the words, "technical consultant required...?"
Anyway, it definitely sounds like the SD card you're trying to salvage files off of is kaput. It's basically impossible to rescue anything off a drive you can't even see, at least at this level of expertise. Sorry 'bout that, but you'll have to break it to her gently, and then suggest perhaps 2GB SD cards, or even 1 GB cards so she won't have the temptation to load every image ever made on one card. Suggest (gently) that she download to her computer after each shooting session, and backup all her photos at least once a week to a different medium/hard drive. All basic stuff, but perhaps much more apparent now after going through this...