There's something not right there. Some corruption somewhere. Have her remove all photos from the phone to somewhere safe on computer or in a cloud app like Dropbox.
Remove all 3rd party photo apps.
Then do a hard reset.
Hold the top or side power/sleep button and the home button at the same time until the Apple logo appears, then release.
Then add photos back one at a time. Add the photo apps back one at a time. Take photos and check them. If you see any more gray pictures, take it to Apple.