You have three options:-
1). Get your granddaughter to unlock it
2). Restore it to factory settings
3). Take it to a computer repair shop who will carry out option 2
Beyond that, we can't help. You're asking for help to bypass the security protocols of a machine which you have no way of proving to us you have any right to be accessing. At the very least this is hacking, possibly with theft.
And it's against
Tom's Rules for us to help