This really illustrates how much her tutors fucked her up. Like, she apparently has always been able to feel out the emotions and meaning from animals and other ponies like this, but she never felt comfortable asking anypony about it due to the abuse.
It seems she was the chosen one. She had the innate powers, she had the societal-position.
Except rather than being corrupted by the darkside, in the OTL she was hurt badly by the failings of individuals and gave up as anyone else would logically do at such a point.
Also with how much Cognitive-Dissonance I am reading (when she removed the pendant) I both feel like this whole situation is still a tragedy despite the worst case scenario having been thoroughly avoided and I feel concern.
I overcame my own maladaptive delusion because I was willing to thoroughly question my own beliefs and give up said beliefs if my beliefs were both false and that getting new beliefs would give a personal advantage.
However, I am used to failure: from that comes my ability to *accept* a loss and try something else.
Sunset is not used to failure. She is used to pain and disappointment, but not outright failure. Thus rather than thinking on things and preparing herself if she is wrong, she's digging her psyche deeper into this pit out of a sense of pride and self-righteousness.
Self-righteousness because ultimately this situation was a series of unfortunate events: Celestia didn't manage things regarding Shimmer correctly and failed to realize this anger was born of deep insecurity and hurt.
Right now, I believe part of Sunset's justification and rationalization for events is that she believes things were calculated on Celestia's part, that there is a point to her suffering: that there is in fact meaning inherent to Celestia's mistake.
Except that is not true: it was a genuine mistake and Sunset ultimately suffered for no one's gain.
When she is forced to confront this reality: that is what will make or break her.