Honestly, Hama's survival can go either way. Even in real life, headshots aren't necessarily fatal. I remember reading about a woman who got shot in real life by her crazy ex in a murder-suicide attempt, and she was able to call the police and made herself tea while waiting for them. Turns out the bullet basically passed through the most harmless path in her brain, so it did no brain damage.
If Hama survives, it will probably be due to something more gray. And given the thing about Hama's brain having overlapping brain scans due to her mother, that may very well tie into how she might survive or revive. After all, there are other lethal spots to shoot, but that bullet was aimed at the most "gray" part of her.
So: I'm optimistic she can survive this. Can still go either way, but the odds aren't the worst.