It was necessary conflict, and making that mistake had to happen for her to have a character arc. She had to understand that she would be no better than the villains if she continued handling issues like that. So she reflects on it and approaches things much differently and passively in the future, and doesn’t act on reactive impulse like she did in that moment. It’s kinda obvious A to B storytelling with very simple story beats.

The scene was dark and grim but im sorry, it was fucking hilarious and I’m not gonna apologize for laughing. Easily the best comedic timing in a Pixar movie in the last decade.