Try resetting her iPhone. This won't remove data or settings, but it might help with your problem.
To reset, press and hold Home and Power button until the Apple logo appears. Let go of both, the iPhone will power up on it's own.
I've tried but the problem persists, when the locked screen it's on and the second keyboard appears on top of it i can still put the code(pin) but it uses the second keyboard not the default one, very strange!!!!
On the possibility that something in settings is causing the problem, try resetting all settings. Go to Settings>General>Reset>Reset All Settings. This will not delete any data but you will have to re-enter any passwords for sites that normally remember you.