So I was in Lumiose city, I entered a building (cant remember which....) and this girl came beind me and said YOU R NOT THE ONE. I screamed...Can someone tell me how I can fix this?
This is not a glitch. Game Freak put this in as a joke and to get theories and discussions, so more people would buy their game.
No, this is very normal. It happens for everyone, and people think she's an easter egg or related to an event. She doesn't do anything else, so there's nothing else to say.