[witchfan]

I'd say Lambda has the power to do anything she wants as long as her board tells us something about Rokkenjima Prime*. If you think about it, the addition of another person to the island isn't too different from killing different people in the first twilight, or assigning them different roles, and it doesn't really affect the core of the mystery as we know it.

Additionally, Erika could be seen as an entity (despite being furniture) in the meta world, but a human piece in the board, and as such she has external influence on the board but is also an internally consistent human piece. A good analogy is a roleplaying game. We have pieces controlled by the game master who exist only in the board, but fellow players have characters both outside and inside the board. If you think about it, in a roleplaying game, there's nothing stopping your character from breaking the fourth wall. But we usually don't do it because it harms the spirit of the game.

Although, this isn't to say Erika can't symbolise something else (e.g. Yet Another Yasu Username ; -) in addition.

*Edit: to clarify, I don't think she'd be able to change the board in a way that changes Beato's core mystery. For example, if the same conditions as the Rokkenjima of EP1 occurred, but nobody was killed.