When Delusion!Carmilla appears in Gabe's little... mind... castle... place/thing, she appears in her Brotherhood of Light robes, but with a villainous air, and a personality that doesn't even really resemble the version of her that Gabe met years before.
Gabriel never met her when she looked like that-- that was literally decades before his time. The version of her that he did meet looked very different and aside from showing MASSIVE cleavage had a very regal and restrained bearing until Gabe actually fought her, when the gloves understandably came off. She certainly made veiled use of her sexuality to try and dissuade Gabriel from opposing her, and then made very plain during the fight she intended to force him to submit and become a replacement for Olrox and Brauner (whom he had killed shortly before), but at no point did she really show much of a sexual interest in him or a particular single minded obsession with him.
Then in Lords 2, she appears in a Castle in Gabriel's mind in a shape he'd never really seen, with a personality with major significant deviations from the actual person he'd met --this Carmilla was obsessed with either having his love, or, failing that, using him as a twisted boy-toy. She's sultry, flirtatious, and quick to anger, and has none of the regal posture or bearing held by the Queen of the Vampires.
All I can imagine is that this is in no way Carmilla, or even a memory of her held by Gabriel, but actually the Inner Dracula spirit taking a voice and appearance the Castle remembered to try to block Gabriel's redemption. The only real similarity with Lords!Carmilla is her fighting style, which brings up interesting implications for another post.
I don't think it's Carmilla, and certainly not a delusion of Gabe's. A delusion would only have the contents of his memory to work with, and this is certainly not beholden to his memory, no matter however flawed it and distorted the Crissaegrim might have left it. Inner Dracula (who is pretty well established as the Castle's magic and spirit taking a defined shape in his psyche) making an early appearance using her voice and shape seems the most likely option here.
So, Lords of Shadow 2 Carmilla is actually the Castle.
Because only in the crazy effed up shared minds of Cox and Alvarez could that make sense.
Thoughts?