Are you in the "cellar" of Bodhi's lair? There are a number of times in the game where Bodhi is unkillable, the final fight takes place in the rooms down the stairs of her lair. She will only turn Jaheira (Aerie, Viconia, Anomen) into a vampire if you are having a romance with her/him, and if the romance is in the right progression stage.
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Melusine, Archbabe of the OHF and the LH
Your voice is ambrosia