>>54156926It really was probably just this. She had access to a decently rare Pokémon few trainers in the area had any hope of countering, and she had the talent to figure out how to exploit it. All of the real players who struggled as kids confirm this. In the first couple of generations it's pretty clear that most of the challengers Gym Leaders receive are local trainers with local shitmons.
>>54156991I like this answer a lot too. Whitney wouldn't have become a Gym Leader in a place like Galar or Paldea where the Gym Challenge is a widely popular event broadcast throughout the region. I don't see Brock, Misty, or many others making it either since it really just comes off as something they do in their free time rather than a primary discipline.