I imagine her Japanese voice sounding like this: http://yanderesimulator.com/Japanese.wmv Slightly high-pitched and girly when she is acting innocent, and a bit deeper and more breathy when she doesn't need to hide her true self.
I think that she will stay how she is, maybe with just a few minor modifications or original assets that try to duplicate the current look.
Since the official site already portrait her like this and Yan-chan is widely known using the white seifuku and ponytail design...
Not just this subreddit, most of the internet has turned against him because of rumours and misinformation and other pointless drama. If you really want to know the details, check out YanDev’s iteration of it and his own side of the story: http://yanderesimulator.com/debunk/
The game's already out, just in alpha or beta. I played an early release of it years ago, it wasn't fun enough to play for more than a few minutes, but there wasn't anything pornographic about the game at the time. You might try it out see if it's suitable, then if it is let her play it, and she'll be bored enough that she forgets all about it and never searches it again. http://yanderesimulator.com/dl/latest.zip
I'm pretty sure Yan Sim isn't for kids. As shown in one of the questions at the bottom of the page here, Yandere Simulator's developer is currently aiming for a "Mature" rating, and the game will possibly receive an "Adults Only" rating. However, the graphics are quite misleading and it may seem like a children's game at first, so perhaps you may want to double-check every game your child downloads before she plays them.
Wheelchair man is not the CEO. If you look at the direct images the wheelchair man's image is called "Founder-Full". The Mr. Schnee looking motherfucker says "ceo-full". That being said it's not at all unlikely that "Founder" and "CEO" are in cahoots.