My undrerstanding of this is there are two ways I have seen it spelled and arguments on either side.
Psychic vampire (psy)
psionic vampire (psi)
I like psionic better because of the fact that is truer to the greek psi which is a character that describes the mind and processes ascociated. to me the term "psychic" is more esoteric than anything, while psionics is a parapsychological term.
so y'know. psionic is like a practice that can be observed by those who know how to observe it, and can be learned and practice, while psychic is something like a 900- (inbound telesales) number for a mysterious woman with a Bahamain accent.
If hairs must be split about it. What do you all think?