The "Mina really loves Dracula" thing is a remnant from the stage performances of Dracula where the character got turned into the romanticised Vampire we're all familiar with today. Of course in the original novel the aforementioned blood drinking incident is basically a rape scene and Dracula is a vile exploitative creature, not the tortured romantic anti-hero most films and other media tend to portray him as. What strikes me as funny in the Coppola movie is that they actually show him laughing about kidnapping and feeding his brides a baby yet they still play him as a romantic victim-hero.
Actually, while Dracula's image was certainly sexualized gradually and subtly over time, the root of the romance lies in the old soap
Dark Shadows, its creator Dan Curtis, and a writer you guys may be familiar with named Richard Matheson.
Dan Curtis made a TV movie adaptation of
Dracula in...shot in the dark, 1973, starring Jack Palance. Richard Matheson wrote the screenplay. Now, Richard Matheson wanted to add a little depth to the Count, and Curtis, not one to care about rehashing things, basically worked in a subplot wherein Mina was actually the reincarnation of Dracula's one true love. This subplot was lifted from
Dark Shadows, with Barnabas Collins instead of Dracula.
Ever since then, as others inspired by the film managed to work in that subplot into their own stories, it just stuck. To this day new interpretations of
Dracula are released in which Dracula and Mina are lovers. I much prefer the Count to be more of a monstrous, pure evil sort of figure, myself. A tragic past can work sometimes, but it shouldn't be used to excuse his evil actions in the present and turn him into a big teddy bear, or worse, a fanged Fabio.