Okay headcanon (very silly):
Carmilla as a book doesn't get mentioned in die erben der nacht but not because Ulrike Schweikert just didn't know it or didn't want to include it but because like Dracula Carmilla Karnsetein is a real vampire in their universe who was supposed to get relevant in the books after Oscuri that didn't ever see the light of day.
She's kind of like the reprouvés of the Pyras and basically is a Dracas (based on nationality and looks) who decided to move to Styria a few centuries back (or maybe it were family members of hers depending) and who just hates all their asses partly because they're from Vienna ( @godthisbitchagain I am using your headcanon from some older post here I hope that's alright) and who would be relevant for something and therefore searched out in her Schloss or whatever by our squad some time post canon.
Due to there not being a Laura at that moment, she makes an effort to seduce the next possible blond woman in sight—Alisa, who then finally realises that she really is into girls. Carmilla has fun in it because she genuinely likes Alisa, and she especially likes pissing off Franz Leopold as a local Viennese asshole vampire. (It turns into a who's the biggest cunt competition very quickly)
However, it doesn't really last, and she wants to go her own way again away from other vampires like before, and so everyone eventually leaves. Alisa with new knowledge about herself and Franz Leopold with a new opp (he's never setting foot into Styria again, let alone with Alisa)
*end of headcanon*
alisa and leo have broken up again, due to another bullshit misunderstanding (those happen every couple years for them and EVERY TIME they are convinced the other one doesn't truly love them anymore, the rest of the gang doesn't even try to help them anymore because it's useless either way)
alisa and carmilla have a genuinely unhinged situationship for a few months that ultimately leads nowhere because carmilla is into the whole human-damsel-in-distress/vampire-causes-the-distress thing and alisa is just way too headstrong to play along with it.
ivy (who is alive again) is the only one focused on solving whatever problem it is they're actually there for, but takes time out of her busy schedule to explain to carmilla how to turn into animals, turns out styria has quite strong leylines, that's why it's the green heart of austria (the gang and or carmilla are responsible for that becoming styrias slogan)
