It's true that Dracula battened on Mina, just as he battened on Lucy. It's even true that he's a sexual symbol. Note the word symbol. Whatever vamp lore has come to in Buffy, good ol' Drac's invasion into people's bodies was limited to his teeth, which symbolized other parts of the anatomy. And what he was symbolically doing was, you know, rape. He mesmerized (read: drugged) women and then took advantage of them, Lucy because he could, Mina in order to hurt the band of Fearless Vampire Hunters.
Mina hadn't met him. She wasn't in love with him, or wishing Jonathan was more like him. She didn't want to be attacked, and wasn't enticing him by showing her ankles under her Victorian skirts. That would be rape, as far as what the symbolism of the attack was. It can cause problems in a marriage, I'm sure, but it's not an affair, and does not generally provide a great start to a lasting and meaningful relationship between rapist and victim.
Oh, and symbolic rape does not produce real children, kthnxbai. In this case, it produced a half-vampire who was Mina. Mina's children--and I suppose this must be shocking--most likely belong to, you know, Jonathan. Her husband? You know, the guy we first met traveling to the Carpathians? The one Mina is absolutely nuts over, to whom she wants to be a helpmeet, who values her because of her intelligence and industry? What did poor, nice Jonathan do to deserve being treated by Drac-fandom like a cuckholded shmuck or an evil interloper? And what did Dracula, who was offstage for most of the goddamned book, do to warrant this romanticizing?
I think Jonathan and Raoul (from Phantom of the Opera) need to start a support group. Buffy's Riley can join it. And Cosette, from Les Mis, as well. And Ron Weasley. :headdesk: