I'm happy I'm not the only one thinking this. Diana is just very serious about magic and her studies and along comes Akko who expects that magic will everything for her so she can achieve her dream. Diana doesn't take this shit, and doesn't hide that fact. But she is never mean to Akko, never belittles her, she only tells her the truth and more than not actually wants to help her.
It was actually pretty annying how Akko almost never seemed to learn she needs to study and practice to achieve her goals. And her screw ups helping her and the shiny rod enabling her thinking process because when she used it were the only moments she did actual good magic. And it can be said that without the shiny rod, she would be nothing.
You could argument it's because she lost her magic but Diana is proof that practice, studying and passion will even fix that.
But I guess this all falls into the cliche anime trope of making your MC useless and just run on pure stupid and 'just do it' attitude instead of training/studying. Can we please stop this.