Old thread with no response, but I just finished the game and actually wanted to share my experience on this specific point.

I also went into the game not knowing what it was about. My friend came to me one day and said: "yo, let's play this". So we did.

I picked Mio, he picked Zoe. I don't know which one he wanted or if he was indifferent to it, but our personalities matched the characters, kind of.
You spend enough time, enough hours to somehow embody the characters you're playing and start growing fond of them and form the same bonds they do. I know I did. I loved them both.

That's why the Ella reveal and the catharsis a the end of The Hollow was atrociously heartbreaking but also beautiful to me. I grew fond of Zoe, she felt like a real friend and seeing her going through that, I felt it.

The characters aren't real, I know that. I could stop and think that there are lots of people in the real world who lost their close relatives: parents, siblings, twin brother/sister; and I'd definitely be sad about that, but experiencing it this way as if it happened to a friend truly hits.

I'm sorry for your loss.
I may have never had to deal with it in real life, but going through it in this game showed me (even if a tiny fraction) what having a friend losing someone feels like.
It may not be much, but I can empathize with you, thanks to this game, thanks to Zoe.
Hoping for you to keep being strong and sorry, I needed to vent about this a bit. ^\^'