Hi! Let's take things one step at a time.
First, can you still access the internal "SD" by booting the phone up and plugging it in to your PC?
If so, back up all your wife's files from there that you want, or you can use an Android file manager like X-plore and copy everything from internal to your external SD.
Then find the stock ND8 tar thread in Development and use Odin on your PC to flash the 1.5GB tar that's inside the zip you'll download.
From there she should be set unless you want to go to optional efforts of flashing a custom recovery, rooting, etc.
Hey that far at least, though, first.
Sent from my Sprint Samsung Galaxy SIII with M.O.A.R. v9.0, dkp kernel dated 3/20/2014 and TWRP v220.127.116.11.