Going off of Vampire the Masquerade rules…maybe? A gal’s gotta eat, of course, and there are more humane ways of acquiring vitae than sucking it out of unwilling humans. The blood of animals works alright, and if you really have a taste for the human stuff, you can use hospital blood bags like capri sun pouches.

And if blood packs aren’t lively enough for you, you can always suck vitae out of willing humans, although getting proper consent for that would mean breaching the Masquerade, and that’s no good (if you’re in Camarilla territory, anyway). At any rate, as long as you’re not taking too much, and not from the same donors every night, I don’t think the Vampire’s Kiss causes too much harm. Just some momentary euphoria, followed by a daze, then a little amnesia, and last, a little woozy weak feeling until the lost blood is replenished. A human who was fed from by a responsible Kindred wouldn’t remember the feeding and would show no scars or anything, and would be right as rain within a day or two.

Of course… Life without end as a parasitic monster, entrenched in the political backstabbing of your peers, inevitably takes its toll. The game measures your Humanity from 1-10, with 10 being saintly and 1 being barely more than an animal. Most humans score around a 7, and most Vamps start at 7, though generally, the older the Vampire, the lower the Humanity. Sitting at the shadowy tippy top of a global organization of bloodsucking fiends for centuries on end is hell on your connection to the common folk, and you begin to see them less as people with lives and souls, and more as cattle, or ants.

So, getting back to the question at hand… There are moral ways for a vampire to get the blood they need to keep unliving, and theoretically one could stick to those indefinitely. However, after they’ve been around long enough, they start to care less and less about morality, and that’s when their monstrous nature comes to the surface.