Considering all these points and after connecting the dots, Kalliope came to a conclusion that the demon and the owner of the voice was somewhat connected, since she couldn't think of any other logical reasons why she had been chosen out of all people.
The owner of the voice definitely knew who she was or she wouldn't have picked her to prevent the Earthlings from their doom. Like the second prince had informed her just now, her magic was different from them. It was a lot more powerful beyond what they could imagine and they even made it their main objective to study her magic because of the power it could grant them.
The magic of the old religion, as the Earthlings had called it, was treated like an ultimate weapon when the people back in Zarronium didn't regard it as anything special. It was simply magic to them.