It does work, and works with virtually no flaws.
You know, other than
every single bit of Carmilla's actions and in-game dialog being absolutely different, both in tone and goals, to what Le Fanu wrote. They're two different people. You're disregarding much of my post wherein I ultimately disagree with you.
So, to illustrate my point, let's break down the key differences.
Carmilla in the games is practically Dracula's Third Officer. She seems to come just below Death in terms of loyalty. She's obsessed with him and just about worships him like a god. She preys on men as well as women; Carmilla in the games is not at all choosy about who she targets. She's a complete zealot for Dracula and whatever cause Dracula supports*. While she is sometimes accompanied by a servant named "Laura", there is nothing to indicate that this is anything other than a nod to Carmilla's literary inspiration. In the games where Carmilla is a major mover and shaker in the plot, Laura doesn't even appear as an unnamed enemy mook.
Carmilla in the book
exclusively targets girls, preferably those who are around her own age when she was turned. She has plenty of opportunity to prey on several male characters in the story and pays them no mind at all. This pattern plays
a huge part in her eventually being discovered as a vampire. She fixates on Laura in a number of ways, including sexually and romantically, because she yearns for an eternal companion she feels will "get" her. She's looking for what she believes is her soul mate. To that end, she also protects Laura from harm, and it's nearly impossible to think of a situation in which Carmilla would knowingly endanger Laura for any reason.
In the novella, she also seems to be compelled to attempt to maintain the experience of her lost youth by living it over again with and "through" similarly aged girls who are similar to how she was in life, like a phantom doomed to repeat itself through eternity, which is part of how vampires were often portrayed in that era: ghosts who never lost their bodies and now exist as twisted versions of who they were in life. She is also very much a noncombatant, preferring to achieve her goals through establishing and manipulating emotional ties, though she does on rare occasion use her ability to transform to frighten or intimidate.
Hell, the only game to even
attempt to visually depict her in a manner similar to the novella was Circle of the Moon, which isn't even part of the official timeline, and they still aged her up considerably.
So no, they're really nowhere near the same character. Their methods and motives are completely different and have little to no resemblance to each other.
We have two distinct Carmillas, two utterly different characters who share a name. One is the original, created by Irish author Sheridan Le Fanu in 1871. The other was created exclusively for Castlevania: a genocidal zealot in the service of Dracula who looks, talks, and behaves very differently but has an occasional conceptual reference to the original character from whom this character draws her name.
And Castlevania's Carmilla would
totally be the sort of type to do what Nagumo has postulated. Whether she actually did is up for debate (I guess hence this thread), but this is definitely not a scheme she'd be above attempting.
*It's a shame we never got to see Carmilla meet Soma. I do wonder what she'd say and do when she realized who/what he really is.