If a psi-vamp were to drain someone (wittingly or no) too deeply repeatedly over several years, and thereby create a "sympathetic" vampire, would that person thus be imbued with the ability to psi-feed? Or, if they didn't have that ability innately, could/would they be forced to turn sanguinism in order to heal the damage done?
If this was done during the person's formative years (say, ending at puberty), what effect do you think this would have on their personality, or what psychological effects might it have?
--------------------------------------- It's easy to be open-minded when you're one of the things people don't believe in...
Now that's a fairly complex question. In effect, it's another theory along the 'turning' question lines.
First off to the psi-feeding ability: I am reasonably certain that just about anyone, vampire/otherkin/whatever or not, who has even a little psychic-type ability (or perhaps even as far as simply sensitivity) can learn to psi-feed in the same manner as psi-vamps. The ability to draw in energy in no way defines, or is limited to, vampires. What seems to define us is, instead, the need to.
In your example, the person fed on too much too often may develop a temporary need to draw in energy from an outside source. Some would argue that this would mean they 'became' a vampire. However, the real question is what would happen if that over-draining ceased. Would it develop into a permanent need (the way some people develop hypoglycemia if their bloodsugar is too high for too long, and their body starts recognizing that too-high level as 'normal') or would it go away? If it stays, then arguably the person has, in fact, become a vampire, at least of a sort. If it goes away, then I would argue no... which is not to say they wouldn't still feel as though they needed to feed... but at that point it would be addiction-need, not 'real' need, if that makes sense.
The real question I would worry about, though, would be the physical/psychological effect that much draining would have on a person, especially if they were unaware of the draining. It would end up that they would show many symptoms of something like chronic fatigue syndrome, without there being any apparent reason for it. This could easily lead to them, being exposed to the right information, to think that they are a vampire, when in fact they are the victim of one.
"We wear the mask that grins and lies, It hides our cheeks and shades our eyes."