I'd think folks would learn to recognize character behaviors by now. Hon is tsundere. She's not a good cook, so she's ashamed to try working with her grandfather. She speaks aggressively to try to hide her shame and embarassment. Also, yes, she wants to be a fashion designer: there's nothing wrong with a kid having her own dreams.
Then someone showed up, stole a present that was precious to her, and started cooking food that clearly affected people's minds. She thought something terrible was happening to her grandfather, and so when the fish showed up and "confirmed" it, she jumped at the chance to save him. Yes, she acted rashly based on false information, but the one at fault here is the fish who deceived her. She's just a young, desperate girl who's afraid for her family.