Hot answers tagged factory-reset
So you have resetted the device? Or was the resetting to factory defaults not working? Boot into the recovery ( volume UP + power button - press both until the screen turns on and release the power button then) and then perform a factory reset from there. This should delete all user data and your phone should restart to the initial startup configuration.
If your sister has access to Google account, she can try the Android Device Manager and do a "Lock and Erase". You may need to enable Lock and Erase first. https://support.google.com/accounts/answer/6160500
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