If Fira were allowed to be her true self on Origin, she would be
The Fourth-Wall Observer. Normally, a BIG part of her character is that she is at all times aware of the Fourth Wall, she knows that I exist, she knows that the world(s) she's in is not real to the Audience, etc. She CAN die, but in a normal setting (not Origin), she knows that if she dies, she's just gonna "respawn" either back into the world she was in, or she'll "come back to life" in a new world.
EDIT: In Origin, to maintain fairness, Fira's not allowed to know that the world is fake, but her basic character is the same, including a strange lack of fear in dangerous situations. She still feels pain, and, as I said, she can still die, but she is much better at blocking pain that others, and her survival instincts, while still intact, are much weaker than most other characters.