I suspect whatever was going on with Coleridge was satisifed by writing the sexy bit, hence his failure to complete it. Tupper's Geraldine is bit ghastly, but provides a rationale in Geraldine being the daughter of an evil hag, Ryxa, and that she has it in for Christabel for stealing her boyfriend. A deal has been written about what Coleridge might have meant by Christabel (see Coleridge's "Christabel" and the Phantom Soul and Samuel Taylor Coleridge's Christabel: Vampires and Transsexualism) but it boils down to being the first lesbian vampire story. Geraldine may not drink blood, but she's certainly a psychic vampire of some sort. Christabel is widely credited as the inspiration for Sheridan Le Fanu's 1872 Carmilla. Apart from in turn inspiring Bram Stoker's Dracula, Carmilla herself inspired a long line of largely naff lesbian vampire movies of which the 2009 comedy thriller Lesbian Vampire Killers is the latest (for others see Top 10 lesbian vampire movies at Den of Geek). Wikipedia's Lesbian vampire article cites Vampires & Violets: Lesbians in Film (Andrea Weiss, 1993) - see review - in viewing the trope as a coded means of handling the taboo theme of lesbianism outside the heavily censored realm of social realism. I don't know. That seems plausible for early cinema, but the persistence into the period of exploitation genre doesn't seem to be anything as subtle.
This is mainly an excuse to segue into a list of my personal favourites in the vampire movie genre. Emphatically not Interview with the Vampire: The Vampire Chronicles (I found the film a drag and the Anne Rice book even more so), nor Bram Stoker's Dracula (highly competent as an adaptation but suffering from Hollywood's perpetual obsession to add backstory and upbeat endings). I've no opinion of Twilight or the original Stephenie Meyer book, having seen neither; but I'm happy to accept the recommendation by Olivia (who works here, and is not stupid) who tells me the book is very good, a thoughtful novel using vampirism as a metaphor for teenage alienation. The list, then, is of movies that break away from the usual vampire-movie fare. All of them, except Mr Vampire, weren't box office successes on initial release, but have since acquired cult status.
- Mr Vampire (1985). A highly inventive comedy horror made in Hong Kong, merging martial arts, Chinese mythology and Western vampire tropes (for instance, sticky rice replaces garlic, and the vampires are hopping Jiang Shi). See trailer.
- Near Dark (1987). The vampire mythos transplanted to modern rural US Midwest, with vampires (never named as such) as a travelling group of outlaws into which a farmboy is initiated when he is "nipped". It's directed by Kathryn Bigelow, who wanted a Western that broke away from convention, and the strong cast is drawn from James Cameron regulars (Lance Henriksen, Jenette Goldstein and Bill Paxton). Again, it's fresh and inventive: caught in a motel during a shootout, the band find themselves in deadly danger not from the police bullets but the shafts of sunlight let in by the bulletholes. See trailer.
- Shadow of the Vampire (2000). A lovely conceit retelling Murnau's filming of the classic Nosferatu, in which Max Schreck (playing Count Orlok) really is the vampire he portrays. Murnau keeps this from his cast and crew with the fiction that Schreck is an obsessive method actor. See trailer.
- The Hunger (1983). OK, a bisexual vampire is a central character, but that's incidental to this beautifully stylish, modern-set examination of the ennui of eternal life. It introduced me to Schubert's Trio in E flat, Opus 100, and I've yet to hear a better arrangement. See trailer.
- Lifeforce (1985). Much ridiculed for actress Mathilda May's permanent nudity as an alien vampire, it bears not too much resemblance to its source Colin Wilson's novel The Space Vampires (itself drawing more than a little on AE Van Vogt's Asylum). Nevertheless, Lifeforce is a taut Quatermass-style SF thriller about an apocalyptic contagion designed to funnel life energy from the whole of London to feed the occupants of an alien spacecraft. See trailer.
(This topic surfaced from the sludge in response to twin themes of vampires and squid raised in the fossil squid story. The umbrella-like section of the alien ship in Lifeforce is rather clearly based on the tentacle section of the Vampire Squid. Its name, Vampyroteuthis infernalis - "vampire squid from hell", not to be confused with HG Wells' Haploteuthis ferox - is rather undeserved; while it's a bit scary in appearance, it's a marvel in its multiple adaptations to live in dark, cold, and almost foodless and oxygenless waters. See videos from Planet Earth and National Geographic).