Since I have too much time to look into the lore of 2hu characters, I found something that I guess answers a bit more of your questions (From Strange Creators of Outer World)>However, Koishi had learned that this ability was disliked by others, and closed her third eye in response. Instead, while she lost the ability to read minds, she also gained the ability to act unconsciously. While she's in this unconscious state, Koishi has a weak presence and it becomes difficult to recognize her, even if she is in one's field of view.
From how I interpret this, Koishi has a "conscious" state where she has emotions, processes events that she does while "unconscious" as memories are subconscious and so on and so forth. Since this is the most "updated" bio of Koishi, it's the best we got when it comes to figuring out this character.
That being said, she probably spends a vast majority of her time living "unconsciously" that its likely nobody even knows that she still has a "conscious" side, not even her sister.