Try closing the Camera.app by pressing the home button.
Next, open the app switcher (multitasking pane) by double clicking the home button.
Press and hold the Camera icon until it starts to jiggle about.
Tap the little red circle that appears on the now jiggling icon to actually close the app.
Now reboot the iPhone (press and hold home+sleep buttons) and ignore the slider that appears.
After the reboot try to open the camera again. And tell your friend to get used to not using the frontal camera and to ignore the switcher button.
The phone does not need to be restored every time.
Question: Is the phone jailbroken?