What is it? Could I not?

The Sonozaki sisters are some of my favourite characters in the series but i was wondering out of both of that who do you like more. I love Mion but i like Shion a little more because of her character and reasions with in the story. ...

This might be an interesting read for series vets, because I'm just now reading this series for the first time with these rereleases. However...I noticed something really strange. Probably overthinking things but...that woman with the photographer...her laugh is the same as the "demon". Possible connection? Who knows. All I know is, I'm ready for chapter 3. Please don't spoil anything for me :P...

As we know, it is Shion who pretends to be Mion all the time. Now at the end of this chapter, we get to the prison where Mion is held (Keiichi thinks it is Shion). I am now at the part where the imprisoned Mion is talking to Shion and saying "..........Mion, my big sister. I beg you [...]" Why would the real Mion call her sister Mion as well?! It is her sister and she should know it is Shion, or did she lose her mind?...

I tried to reinstall the game, repair the file, update my computer and game but nothing works. Does anyone know why and how i can actually solve the problem?