what happen if the world exists a copy of yourself?

Have you ever imagined that someone have appearance like you? I have been heard that there is always one person who look like myself. She live somewhere in the world and have appearance like me from head to feet. If I and she meet together, I or she will die. Of course, this is a child's horror story but if in real, it is a big problem and I hope I am the only person with my appearance.

a copy of myself