Question about the twist...

And why does Red (the one we now know was actually the original girl) tell the tale of the shadow, as if she was the clone? Why does she say that the shadow hated the girl? Why doesn't she straight up say "You are my bizarro copy who kidnapped me into the underground bunkers"? Not to mention that the way in or out of the bunkers obviously was not restricted by any means, and hundreds of people would have come across their clones by the stairs.