1) First, play this game. It's short and pretty, and has nice music. It takes anywhere from 15-25 minutes. It's also free.
2) After playing, come back here.
Post your theories on what the game is about. Don't go "google-ing" this, I'm interested in seeing people's ideas! Have fun!
I'm still trying to develop my theory, I'll post it later, if this thread gets enough attention. This is the best explanation of the game I've found so far:
The Mirror Lied - Q&A [Freebird Games]