Oho, loaded question 👀.
She was told something unexpected at the age of 16, after finishing her journey through Hoenn, which completely broke her morale and gave her a crisis.
She closed off and mood became extremely sour. Because if this, when she began her journey through Unova she was...a short fuse.
Taking out her pent up anger and resentment in those who annoyed her.
This was at her lowest and most neurotic.
She had to be put in her place to calm down and be reminded to not throw a temper tantrum without realizing the consequences of her actions, and what was to be at stake.

Unfortunately...after some reflection at the end of her journey, she closed off even more, but became better at pretending she was just fine.