>>30745352I feel like I've read somewhere that catching a Pokemon in a ball links it to your Trainer ID for it to work in-canon, so her not being a trainer would mean she doesn't have a Trainer ID, and so no way to actually use a Pokeball. Maybe I'm just mistaken.
Or even simpler, maybe Poke Marts can't sell Pokeballs to non-trainers. Like, maybe you have to show your trainer card like a license.