Nanihi Manave (hidden)/theories

Post here all your theories as to why there are two Nanihi Manaves.

Theories
Most likely a meant for the game but was not used in the final finished game.Thats why she can only be seen using the SP.

I know! If she died and you wanted to do the story again, the hidden Nanihi replaces her if the original one dies/grows up. (sorry if I'm wrong I only have sims 3 this is just a guess)