All they need to do is update the Influence Emotion power to cast fear.
There, solved.
The issue with making "scary vampires" (outside of the aforementioned power) is that even those close to said vampire (or another vampire) will get scared if they meet the conditions to be terrifying. Case-in-point: when a ghost (even one that's a part of the household) possesses an object, sims will get a fear moodlet from it. Doesn't matter if they know the ghost, instead of laughing it off or being annoyed, they'll ramp up to being terrified as soon as they start spreading their irrationality.
