I hate protagonists who are incapable of realizing they are incredibly powerful despite it being their supposed area of expertise and having nothing preventing them from realizing it beyond their own apparent stupidity.
It'd be one thing if the only other people she worked with were incredibly skilled mages so she couldn't tell where the average was, but she was number one at the royal magician academy for elites the entire time she was there and has now been hired onto an elite squad protecting the royalty of the country. She has no business thinking she is below average at magic. It isn't like people hide it from her either, literally everyone other than her former boss goes "Wowie zowie, you're just the best at magic!" yet she still thinks she's shit.