I hate making points without evidence to back them up. Recently in this review I've been referring to Nya as a narcissist, so I've researched narcissism to prove my point. During said research I came across an article, from which I will be copy/pasting the nine traits of narcissism to expand on. Here is the source link in case any of you all would also like to read the article. 

Source link --> 

https://www.emedicinehealth.com/what_are_the_nine_traits_of_a_narcissist/article_em.htm

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1. A grandiose sense of self-importance

The most blatant case of this is how Nya thinks she's above Maya. Every time Maya tries to help or share her wisdom with her daughter, Nya pushes Maya away. Nya seems to believe she can solve her problems without the help of anyone else. There's this, and then there's also the beginning plot to this season. Nya's powers are going wacky. Nya's powers are a risk to those around her. She knows this, and yet insists on going on an underwater mission. She apparently has no regard for the lives of her teammates, because if she did, she'd stay behind to let them handle it instead of risking drowning them under the sea.

2. Preoccupation with fantasies of unlimited success, power, brilliance, beauty, or ideal love

Nya barely knows Kalamari, and yet she despises him. Why? He's a threat. Since Nya has made this mission all about her, if Kalamari gains even the slightest advantage, that's an attack on her character. She just mentioned the last episode that "you don't know him like I do", which is to say, none at all. Nya fantasizes about getting rid of Kalamari. Not because he poses a danger to Ninjago, but because he poses a danger to her golden image of being the perfect little Ninja.

3. The belief that he or she is "special" and unique and can only be understood by or should associate with, other special or high-status people or institutions

The fact that Nya disregards Maya and Wu's wisdom for her own knowledge is enough to prove this point. 

4. Requires excessive admiration

If I had a dollar for every time Nya verbally blames herself for something just so other characters can comfort her, I might just have enough to treat one of you lovely readers to dinner. Nya is constantly needing to have her ego stroked. Sometimes she gets Jay to do it. Other times she manipulates Maya. Most of the problems of the season are Nya's fault, but instead of trying to fix them, Nya just gets other people to tell her that she's perfect. 

5. Has a sense of entitlement

See the point for #3 and #1.

6. Is interpersonally exploitative — takes advantage of others

Over the course of this season, we see Nya bend Maya to her will. By ep 9, Maya is completely wrapped around Nya's finger. Nya needs an ego stroking? Maya's there to help. There's also Jay. Most of the time when Jay tries to be a good boyfriend to Nya, Nya physically pushes him away. She may not say anything, but her actions speak louder than words. Basically, Jay's there to serve the same purpose as Maya: tell Nya she's perfect.

7. Lacks empathy

I think the way Nya treats Maya this season is the best example here, but I've ranted enough about Maya. Let's talk about the team. Nya is incredibly rude (and borderline violent) to everyone the minute she does something wrong, because how dare they even suggest she messed up? Also, Nya knows how serious the Keepers are about protecting the amulet, yet she cannot see their desperation as evidence that they should continue protecting it. In her head she is perfect, and thus everyone else is incapable. For more evidence, see #6.

8. Envies others or believes others are envious of him or her

This one's a bit harder to pin down, but I think we can look back to the first episode. Nya gets enraged quite quickly whenever her powers go awry. Her terrible behavior towards the team shows that not only does she have no self-control, but also that she envies that they aren't having the same problems. Why does the rest of the team have absolutely no trouble with their elemental powers, and yet she does?

9. Shows arrogant, haughty behaviors and attitudes

Insults and belittles Kalamari upon first meeting him. Rejects her mother in all forms of verbal/nonverbal communication. Thinks she's the leader of the team instead of Lloyd. Thinks she's a better protector of the Storm Amulet than an island with an army. 

After reading the points of this argument, need I go on?