Here are the steps you should do to recover your GF's phone,
1- download official firmware from Samsung-updates.com (make sure its official at&t firmware)
2- download Odin (this is used to flash official firmware)
3- unzip the firmware you downloaded. Inside should be .tar file. This is the file that must be flashed
4- unzip Odin if needed to, inside should be exe file to run Odin.
5- put phone into download mode (hold vol. Down + home button + power button same time) you'll get a screen where it asks you to press volume up or down to either cancel or proceed to download mode. Go into download mode
6- run Odin and plug in your phone
7- Odin should then recognize your phone telling which port your phone is plugged into (ex. Com4). If it is indeed connected and recognized move on to the next step.
8- press the PDA button on odin, a window should pop up where you can locate the .tar file. Look for the file wherever you extracted it to. After you find it double click it.
9- .tar file should now be in the PDA slot. (Please note that "auto reboot, reset time and pda should be the only boxes that should have a check, make sure nothing else is checked mark) by default the the checks should already be there and you shouldn't have to do anything but I thought I'd let you know just in case.
10- press start and wait till everything is done
---------- Post added at 01:24 AM ---------- Previous post was at 01:23 AM ----------
After some research of my own, it seems that flashing the stock firmware over your phone will not wipe any data or apps as long as you didnt wipe/factory reset your phone in recovery
---------- Post added at 01:30 AM ---------- Previous post was at 01:24 AM ----------
I've taken the liberty in helping you out in providing the links that needs to be downloaded.
Official At&t firmware- http://samsung-updates.com/details/2...37UCUAMDL.html