Amelia is special in that her head opens up for a visceral by breaking her legs instead of the head itself. So, when you do break her head, she has a special animation of clutching her head in pain that other bosses don't have.
We all know how chaotic Wet Nurse's nightmare (clone) phase is. However, if you lock on to her after she twitches her wings and quickstep twice as soon as the purple aura appears, you cancel the entire thing.
For whatever reason, the aura creates an invisible projectile that starts the phase when it hits the player character. But if you dodge it, the phase never happens.