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Apple ID/iCloud ID would be the email address registered with the iPhone. If she don't remember the Apple ID, then she can find it from
here --> https://iforgot.apple.com/password/verify/appleid#!§ion=appleid
If she don't remember the password, then she have to reset the password. She can reset it from here (go to this website from your computer) --> https://iforgot.apple.com/
Go to the above website. Use the "Get an Email" method to reset the Apple ID password. Apple will send the reset instructions to the recovery email setup with the Apple ID. It would be the email registered with Apple, like Gmail, Yahoo etc. Open the email and you will see the email from Apple. Open it and follow the instructions to reset the password.
If that didn't work, then go to this site again --> https://iforgot.apple.com/
This time use the "Answer Security Questions" and answer the security questions there to reset the password.
Please let me know if that didn't work, so I will continue to help you