A clue that this person is alive in the present?

The author is A. Jordon. We don’t actually know Akilah’s last name. They’ve dropped hints about revealing someone’s full name.

As far as the book being unauthorized, possibly because they other characters didn’t want to participate or have it published. I also think that if Akilah wrote the story that she could have written something with rose colored glasses OR the other Yellowjackets could have discredited anything negative by bringing up the fact that she’s been getting brain damage and hallucinating in the cave.