We've seen some other baddies with this trick. The Whampire whispering despair in Elaine's mind... the Fallen whispering "all your fault" in Harry's. Trying to pretend it was their own voices.
And the general "anger issues" Harry was having with the Shadow, pre-Sheila; I think that's part&parcel with the method.
Maybe Nemesis works that way; but I don't think we know, not for sure. But... I'm slightly-inclined to think not, honestly.
mmm, why? Don't remember the original basis, but the current model is from woj about Thomas having a coin and the fact his demon would get the short end of the stick on feeding since they largely occupy the same place in him,
That place would be the mirror, which sets part of why I think the denarians are specifically designed to deny Nemesis power inside reality. The fallen hold the same mirror, representative of the the shadow/subconscious as nemesis seeks to aligned with to reach through and use the same chaotic/apocalyptic power to feed on.
We've seen the "conflicted" model, e.g. when Lea was flashing back and forth between Nemesis-dominated and her own impulses; or when Harry tried to get Cat Sith to break free.
We've seen fully-dominated, with Justine.
We don't really know what we saw with Maeve, or Aurora: were they being "tricked into thinking it was themselves"? Were they in the "fully-dominated" category? Or were they actively & knowingly partnering with Nemesis?
mmm, and I for some of this look at GP and most of the original talking head moments on possession. Lea for instance acts alot like an addict, and I think Jim mad intentional parallel to how Bilbo behaves in LotR. Drunk with power and trying to quit it.
For Aurora I suspect both, she'd made a deal but it doesn't explain a lot about the context of it or who actually set the price. I suspect she knew the consequences of her actions but truly thought it would bring a better world by breaking the cycle. She, like Molly does later, made a promise to herself basically. But... she shouldn't have had that bit of power to change still.. It was never Nemesis she thought she was dealing with... Only Elaine and her emotions at being stranded within the fae courts rubbing off on her. Wizard auras aren't usually strong enough, but what about prolonged exposure to a starborn aura? I think it in itself can elicit change, that Nemesis can take advantage of in creatures specifically designed not to change like the fae.
Cat Sith.. I think Harry opened him to change, and Mab already knew it would. Harry also did something Mab took a possible eternity to do with Lea in minutes.
Justine, is also explained under the lens of possession. WCV's are addicting and she not only basically overdosed but had most of her soul ripped right out with it. It left her vulnerable to possession as would be.
As far as why Justine? Nemesis has a thing for young powerful and mentally unstable(another will weakener) females. My guess is this is her truest possible mirrored form as Nemesis the Name would imply. She has seemingly gone after Lydia, Molly, Justine, Ivy and perhaps im forgetting one or two 🤔 not counting the Sidhe, most of which shes dominated more successfully than say, Sith.
We know Nemesis is subtle, in the "hard for an observer to detect" ways; but we don't know the details of how it approaches & interacts with hosts.
I don't think we've ever seen someone acting "puzzled" about why they did a thing, except a few times from the inside when Harry was realizing he'd had his brain bent (by Mab, or Lasciel's Shadow).
and I'm supplanting that my wall of weird linked together does explain this.
Fate/Soul/luck/active-creation/Wizardy is where Nemesis hangs. If something seems to be a part of yourself, of your own soul or how you've decided to change to be... You wouldn't expect it or think twice huh? We can linearly look at the parallel of how Peabody operated. It nudges you, makes certain thoughts louder. Gets you to make your own choices, Create as you act.(deep parallel here with how magic makes you "more of what you are") eventually that fundemantally changes who you are over time, and as the mirror comes more into focus they have more purchase through it. I don't think she's focusing the mirror just for herself tho, but for her cohorts to have vessels to claim.
Fae, who are Spirit and Body without soul except the bearer, any change in who they are is self apparent quicker with reflection, if caught quickly or not overpowered by change(transmogrify?!?)
Back to Lea tho, and this is the first time plotting this part together.. I account Morgana as being the Arthurian version of Nemesis, and perhaps the most recent physical one.(she's now Mavra I think, but different story)
Leah holds the mantle of the lady of the lake(citation DB summoning intentions) now, something in some stories attributed it as Morgana..
insert possible convergent timelines theory or light/shadow interplay of fae beings to maintain balance being upset
l think between it being Morganna's athema and her holding said mantle was enough to align the mirror for a direct take over attempt. But, like with Sith she didn't take over immediately. It wasn't until she went to confront mab that Mab forced the possession by reasoning with the real Leah still left.