Unfortunately this sounds like she used a different email or password ***** the phone was initially set up. If you can't remember that email and password ***** can reset the phone to factory defaults and set up again.
Try these steps please. With the phone powered off, press and hold these buttons down at the same time: Volume Down + Volume Up + Power key. Next from the menu choose "Wipe Data/Factory Reset", using Volume buttons to scroll to option, and Power button, to confirm operation. Then select "yes", and confirm with Power button.
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