The link below leads to a wonderful Supergirl: Cosmic Adventures fan written story I recently came across. The most striking part for me was how clear the voice of Belinda Zee came through, despite me not having anything to do with this. There's a bit of ego tied in with these characters... they exist in my head. That's where they were born and that is where they will always live.
But that's ego. The truth is that a talented writer can take the characters and bring them to life. As exhibited below:
The scene that plays out, and some of the perspectives held by the characters does not necessarily match how I would portray things. Nor should it. This is a well executed extrapolation from the mind of another writer. I think she does a very good job and I hope she chooses to write more in the future.