>>3465595>>3465645>>3465647However, it's a but complicated from her on out. You see, if Zelda was still conscious during everything, she could cause Sheik to make mistake and get caught. So Zelda is most likely NOT conscious when Sheik inhabits her.
Zelda is essentially a vessel for Sheik. Zelda can't do anything or say anything. Sheik is in control of her body. Now, since Sheik inhabits her body, there is a VERY IMPORTANT thing to gleam from this. Sheik does have access to Zelda's memories and is affected by her personality. As long as Sheik inhabits Zelda, this will always be the case. Sheik is also the holder of the triforce of wisdom now, not Zelda. She has that power. And when it comes to her physical self, she is still Zelda. I believe the triforce of wisdom CAN change Zelda's body to look like a true Sheikah, but for some reason, it didn't happen. You see, the Sheikah are a brown race with generally white hair. Sheik definitely looks darker than Zelda, but it doesn't go all the way. I believe this physical appearance is a MIX between these two separate people.
One last thing makes up OoT Sheik. Sheik had to survive for SEVEN years on the run from Ganon. Sheik had nobody to interact with. Nobody. She was alone. Can you imagine what kind of life and trauma she must have lived through?
When we first see her in OoT, those seven years had already passed. You can tell with how she talks to Link (she talks with a lot of prose, plus she doesn't seem to have much confidence in him) that she has lost a lot of the hope she initially would have had. So these seven years really did affect her. As Link started winning and pretty much was on track to save Hyrule, you can see that she starts to have hope again. She really starts believing in the Hero of Time. This hope does turn into overconfidence when she reveals who she is to Link a bit too early and gets Zelda captured.
This is who Sheik is in OoT. Not what you were expecting, but this is her.
