BADASS. @jkitten usually in these kinds of novels characters considered "pretty" are the cutesy ones with smaller faces and weak looking faces while more intense ones like Melissa's or like Bakarina's in otome hametsu are considered less pretty or more intense in-universe.
Honestly I disagree. Melissa here and Katarina in her own series are both very beautiful and more mature looking than the heroines of their story.
@jkitten I think it's more that she looks cold/sharp/evil, so people wouldn't be charmed by her like they would be someone cute/petite. I mean I agree she's beautiful, but that's probably why she doesn't consider herself "good looking".