In the bedroom scene from the film Bram Stoker's Dracula, Vladimir chooses damnation because he loves Mina so much. It is she who chooses the curse so that she can be with him. If my Fiance was a soul drinker, I would destroy the prison of her existence so her soul could be free. If this meant my death then so be it.
Are we talking about the literary type of vampires or are we talking about humans with vampiric abilities?
I would never even attempt to "turn" someone. Personally I do not think it is possible. IF a person has vampiric tendancies then they were born with them. Literary vampires do not exist but as Krakyn stated, there are humans with vampiric tendancies.
There is a wide range of degree in feeding preferences, as well. Blood drinkers, in my opinion are at the bottom of the scale. They know they need something, and they know they can find it in living blood, but they don't really know what it is they need. For lack of a better word, let's call it chi or life energy. Vampiric feeding runs the gamut of blood, sexual energy, mental energy, emotional energy, elemental energy (people who "feed" off storms and fires and such), astral, and those who can ingest chi without physical contact then there are those who can feed off the unattached chi of the universe or directly from Universal Source. These would be the highest level of vampires and no one would know they were vampires, anyway.
If I were married to a person who eventually identified himself to me as a vampire it would depend on his feeding preference whether or not I would aid that person. For blood drinkers, it has been my experience that their need is often a modest sum and an infrequent usage. I have met a self proclaimed blood feeder who needed nearly a pint every time he did feed but he only needed to feed once in two or three months if he got his full unit. He seldom did, because that's a dangerous amount for anyone to donate unless it is done with proper blood donation equipment. Probably why this person was a phlebotomist. Most of the vampires of my acquaintance were law abiding people who got their donations from volunteers but many of them preferred carefully screened strangers or their best beloved to be their donor as they all claimed a strong psychic bond with the donor.
A word about astral vampires. My personal opinion is that this kind of feeder is the most dangerous. I've told my paranormal students repeatedly that if you die in the astral state you will eventually (soon) die in the material. The astral plane is the bridge between material existance and completely spiritual existance. Astral vasmpires seldom ask permission and their draw often is too strong to allow their "donor" to recover quickly. I've had a personal experience with an astral vampire and if it had not been for the fact that I am psychically stronger than he was, I might not be here now.
Harkon, you are my kinda of guy that sounds romantic and honorable.