You definitely need a WiFi signal for FaceTime. She can tell if she's on WiFi by the symbol on the left hand side top of the screen. The symbol has three little curves at the top instead of it saying 3G the symbol is in its place. This is located next to the carrier name.Well she says she is on interne but not sure if wifi... But ye ill tell her to take off imessages and then put it back on
Sent from my iPhone 4s using iCafe app
Turning the iMessage off and then back on should fix her problem.
Let us know how it turns out.