I feel like she's being needlessly difficult about what is essentially a turn of phrase without deep meaning behind it.
Then again, "needlessly difficult" describes the tsundere archetype rather well.
She's kinda like that in the game, she gets really angry often because she thinks people are looking down on her.
Basically, she's very insecure. Though not without reason, as IIRC her backstory is basically that everyone made fun of her for being too short and even veteran trainers were telling her that it would be too dangerous for her to be racing with such a small body.
