Love will have its sacrifices;

-While the events of the novella more or less applies as something that has happened, the ending is of course different - she isn't killed when found in the coffin, just grievously wounded by the stake almost going through her heart, and Carmilla's Sire convinced her to let Laura be, at least for a few years - when Carmilla checked years later (around 1855), it was too late.
-Which is something of a sore point even today, even if she understand why her mother told her to leave Laura behind. She remains a little bitter about it.
-Carmilla was 18 when she was turned, born in 1680, and is currently around 337 years old.
-She has a mole on her throat, on the right side and a little up above the collarbone.

-Feeds exclusively from female victims (and can sometimes become a little confused and indecisive whether she wants to eat someone or is romantically attracted to them).
-She sleeps immersed in blood; earlier this was often in a coffin, though in modern times she takes to other solutions. As well, 100-200 years ago she'd have used human blood; today it's usually animal such, though she still feeds from humans otherwise.
-Young vampires are confined to their coffins for at least a few hours every night until they are around a 100 (which, for Carmilla, would've been 1798); she was spending a few hours a night in the coffin only every few days while the Laura incident happened, and after this Carmilla, her 'Mother' and Matska left Styria. She does still, like any vampire, need to return to the area she was turned every so often; the older she gets the less she needs to do so and the less time does she need to spend in the area of Styria where she grew up.
-She isn't confined to the night. Morning and noon-time sunlight burns (the earlier, the more lethal), but she can be out during the day in the afternoon, the later the less effect (she prefers to stay inside until two-three at least).
-stake through the heart paralyzes vampires so they appear dead, but full death needs to be by decapitation and/or burning (normal fire or left out for the morning sun). Vampires do not turn to ash when staked or decapitated.

Notes on dates:
-Laura's account of the events to Doctor Hesselius is given eight years after the incident itself, so she's 27, which would be in 1823. By 35 (in 1850), Laura had succumbed to the weakness being fed but not killed or turned had stuck her with, and in 1870 the author (in the real world Le Fanu, obviously) of the book Laura's account was turned into tried to contact her after finding the doctor's papers and found she'd died earlier. In 1872 the book is published.

Powers
-enhanced senses, strength, and speed.
-Can transform into a large, feline beast. Looks very similar to a black (European) lynx.
-Dream manipulation. In particular making her victim believe she's dreaming even when she's not (usually in regards to when she comes to feed on someone, but also straight-up dream manufacture to allow interactions mind to mind).
-Is sometimes capable of passing through walls, but she needs to have fed recently to be doing feats such as that (or having soaked in blood for a while, hence why passing through the walls and whatnot in her tomb can be done).
-Revealing the full force of her predatory nature (usually cloaked) often stuns the target with animal fear and they become pliable/easily suggestible.

(-Carmilla is moody, and has a rather easily provoked temper. She tends to snap, scowl and yell when she gets angry. Only very seldom does she become physical, and in that case it's more slamming a fist into something like a wall or table.
-Religion is a rather touchy subject, both because of her own guilt regarding her (former) belief and inability to practice it now, and being wary/angry about the damage faith and faith-charged icons (no particular religion) can do to her.
-Nonetheless, she can be very sweet, romantic and charming when she feels like it or is taken by some particular girl or woman.
-Despite her temper, she is surprisingly patient otherwise.
-She tends to get possessive, regardless of if this is about prey (since she tends to choose one and feed on them for a while, which can lead to death, or not, depending on how long she does this), or a purely romantic attraction.)