Nessa was alive, this was no secret or surprise. With his most powerful attack, Plague Reaper was able to wound her badly, never in her life had Nessa faced such bloody and serious wounds, but the fact that she was a Hybrid saved her.
Her body was stronger than any K1-Phantom's, most likely even many K2-Phantoms would have died if they had been hit by the hail of red jaws that tore chunks of flesh from Nessa.
There were many ways to die, but being eaten alive was probably one of the most painful, but Nessa was lucky. She got her fair share of hellish pain, but not death.
Her weakened state had been taken advantage of by a random monster, one of the few Light Yellow Threat ones that still survived within the flame ring.
But... It was a fatal mistake.
Nessa was badly wounded, but she was not dead and remained conscious. She wouldn't have moved in any other situation, but her life was on the line when the monster attacked.