She might not have used her freaky mind powers on John of her own volition, and that there might've been a little psychic reacharound acton going on here. THINK ABOUT IT: Doc Scratch is nigh-omniscient, and whatever he doesn't know or can't figure out for himself he doesn't or can't because his ignorance is necessary for destiny to do its thing.
He didn't know Vriska had acquired his Magic Cue Ball because it was necessary for him to get pissed off enough to blow up Vriska's face. Seems like an awful lot of trouble for Predestination to go through just to mutilate a little girl, especially considering that she gets her missing body parts back. UNLESS: some of that crazy First Guardian energy also got into her head while it melting off half her face. Something like instructions, or maybe Doc Scratch has a foothold into her brain and can see what she's doing.
Yeah, she has her own insane reasons for putting John to sleep at that critical moment, but Hussie himself pointed out that Terezi's lusus wanted to blind Terezi anyway, and allowed itself to be used to blind her.
