Fingers crossed that part of this creature is actually a shard of the fully sentient aberrant that is her mom?
More fingers crossed that Lacer didn’t follow Oliver to Liza’s and sneak in the door behind him to observe all of this.
I’m running out of fingers, but I’m crossing some more that she wasn’t actively casting that spell for days, through a seizure - and that it was only something she had to actively cast once - so that she’s not casting with Will strain. Again.
Quietly passes Stef more fingers to cross.
I’m…almost certain that part of the chimera inside her head is her mother.
And really, that’s so tragic. Imagine if she were aware in some part of her shattered psyche that she was harming her daughter - psychologically torturing her…but couldn’t stop. Wasn’t in control enough to stop. Maybe even resented her for not remembering her, even though she couldn’t, even if you logically knew she shouldn’t.
There’s so many layers of awful to all this.
The last book should have had more warnings. 
Because you just know if Siobhan comes to that conclusion - correct or not - that she’s going to go “I can’t kill her! I can’t lose her again,” and double down in finding a way for the creature to survive.
I dunno, I dunno, Siobhan is very motivated by survival and she does have a massive fear of losing her mind and becoming an aberrant.
She might actually be willing to kill her mother to free her of that cursed existence.
Then again…
Death would be the ending of the story of the person I most cared about - myself.
Or words to that effect, I can’t remember the exact quote. She’s not exactly spiritual.