Crit for you, as requested~!
So, let's start with her creature type and natural ability. While there could be a demon subspecies with a particular hunger for knowledge, I doubt that they would be a succubus - the succubus/incubus species are strongly aligned to
emotions. I suggest choosing a different type of demon.
As for the natural ability, accessing great secrets is much too overpowered for a Y1 character in Amityville, and would probably not work out too well in actual gameplay regardless! I recommend picking another natural ability. (While you could go with the shapeshifting, I'm not sure what being a Fennec fox has to do with a demon associated with knowledge? The two don't seem to fit together.)
For her personality, it looks fine for the most part. The one bit that gives me pause is this: "So smart that she literately can look you up and down and know exactly what your in to." How does she do this? This is coming perilously close to godmoding, in which you use OOC knowledge of a character for IC purposes. I would make sure
not to skirt the line so closely... she can be smart, but not infallible.
For her FEAR ability, you'll need to pick a
FEAR mechanic for her! I'd recommend reading that guide. All the development of your FEAR has to be matched to a particular mechanic, so having a good understanding of that thread is really important!
From what you'd listed already, it looks like you're wanting an illusion shock effect. Perhaps Headlights would be a good mechanic for her to use?
I hope this helps you! Good luck with your quest~