The nightmare came to an end,
Catherine had merely shown William her audition at the circus and how her headache had evolved into a nightmare.
In particular, the transformation of the nightmare bore some similarities to William's metamorphosis of a madness brain.
It was undeniable that Catherine possessed talent, but aside from her own strength, luck also played a part.
Had the previous assistant clown not been killed, he would never have allowed Catherine to carry out a mass slaughter and absorption of the dancers while sleepwalking.
Moreover, it just so happened that the clown Art had been detained, not having been indoctrinated with malicious concepts at the earliest opportunity.
At the tender age of ten, with a mind yet to mature, Catherine would have likely assimilated if she had begun following Art from the start. It would be impossible for her to be here having a friendly chat with William, as every motion of hers would exude malice towards the world.