[quote=LeeRoy]
1: The fire is made of matter, the air is made of antimatter, Evvie is made of matter. Everything blows up.2: I suppose light would hurt shadows, but would shadow-air be able to produce lift as she flies?3: That seems mary-sue-ish.
[/quote]

1. There wouldn't be much antimatter floating in space so it wouldn't cause any explosions powerful enough to kill someone like her nearby. However, if the resulting explosion when it does hit a planet or star far away, if as powerful as the Big Bang, would of course kill her even though she can regenerate from a single cell as a demigod.
2. I don't know about shadow air but her wing are augmented with magical strength to help her fly so it might not matter.
3. One must become a Mary Sue in power to deal with certain scenarios. She's not omnipotent or whatever the term is for all knowing, but you have to assume her mind would get a boost by being a demigod. She also regains memories from all of her lives, although that wouldn't help her in that specific case unless she had experience in such a world before.