[Ealasaide]

Right-o, Pio! That's precisely how I see her. You hit the nail (the Naiore?) on the head, so to speak. I think her association with Sauron merely served to distill the socio-pathological tendencies she would have developed on her own over time.

If she were always this way, without the ability to fear, was she at first simply curious about the fear she saw in others?

I would think so. Like with serial killers, the more she indulged her curiosity about her obsession, the more it grew.

Did she at first grow jealous and or hateful of those who could experience the range of fear emotions?

Interesting question! Elora, who originated this character has this to say about Naiore's early childhood:

Naiore was both fascinated and slightly repulsed by other people. She sought few friends and had little regard for the opinions of others....She became fascinated with impulses that many refused to acknowledge existed within themselves... The forbidden nature of her inquiry seduced her further... She became more isolated, and developed contempt for the apparent foolishness of her parents and kin.
...War was bewing over the sea, and Naiore could sense a power growing. It tempted her. Proud and contemptuous of her own kindred, Naiore sensed that many of her forbidden questions could be answered...

Did she invert her jealousy and begin to see those others then as inferior to herself because of their fears?

I don't know that jealousy was ever a factor, but Elora mentions again and again Naiore's contempt for her kinsfolk and her fascination for the darker elements of life, with a particular interest in the arenas of pain and fear. I think there was a definite belief in her own fundamental superiority over others.

And seeing herself as superior to them, learn early to use their fears to control/manipulate them?

Oh, yes. Absolutely.