My options for bought reported as stolen Sprint iPhone 4S

Hi all,

I spent couple of days reading thru these forums and just wanted to confirm what I've learned so far.

History:
My girlfriend bought a "unlocked" Sprint iPhone 4S on craigslist.
Version# 6.1.310B329
Model# MD378LL/A
When she tried to use it overseas it was locked!
I called Sprint and asked if I can unlock so she can use it there.
They checked MEID number it was reported as stolen!

So that means once she brings it back it won't be possible to use it on Sprint network and good (only?) option is to use GPP SIM hack?
Also, I came across swap bad for clean ESN on ebay but I don't feel comfortable mailing the phone ot someone and hoping I will get it back.

If I use GPP option I will able to use it with ATT or Tmobile here?
or send it to a relative overseas to use.

Did I miss any other service?

TIA