AnonymousCountry code: blank.gif, country type: blank, valid: No.36834994
Moondancer suffered, and it was Twilight and Celestia's fault.
She experiences a legitimate and significant depression for long period of time.
Some viewers think it happened too quickly, or that the impetus wasn't significant to cause such a depression.
But here's the situation: she's a shy, introverted, child. Her best friend suddenly disappears and leaves without a single word, ignoring her party - and never so much says a word to her. Never writes, never reaches out in any way.
Moondancer begins isolating herself. Her trust in opening up and getting close to people is damaged. She develops a fear of abandonment. It was a traumatic event, that party.. It can happen like that. She engrosses herself in work and loses even interest in social life.
And why did Twilight leave? Why was Moondancer left behind?
Because Twilight was the chosen one, the protege. One unicorn get sent to Princess Celestia's School for the gifted to.. literally becoming the Princess of Friendship, and the other is left behind to feel like an afterthought; her best friend dropping her without a second glance for, to Moondancer's perspective, the chance to be a princess. Perhaps Twilight was *right* to focus on her studies, and thus Moondancer follows suit. Both were studious, smart girls.
Twilight goes on to grand adventures, traveling the world, meeting new and amazing people, becoming an immortal royal and famed hero.
Moondancer lives in a dark room and shuts out the world. There was no Princess of the Sun and grand destiny to whisk her off.
She deserved better. Sure, in time, Twilight reconnects with her and Moondancer learns the value of friendship again. But she's still had to live through that sadness and lose that time.