The cursed sword makes the body rot and fall apart, her reversal made it so her body heals and comes back together. Though whatever the chimera was doing it, it didn't count as her body either dying or rotting, hence why she had to cut off her own arm to proc the requirements. When she first picked up the sword she was dying from internal injuries and malnutrition after all. I'm guessing the way how the attack worked was it causes the body to contort and twist in a spiral until it breaks and then it takes along more of the body to keep on twisting.