I can't say that I trust her on analyzing difficulty levels. After all, she's the one who for some reason made it a habit to occasionally dress up as an elementary schooler, as shown in this chapter as well. A lot of questions towards her get answered in a suspicious way too.
The term "final boss", which some people may call her, is stereotyped to be difficult; however, this is Bocchi. She's not exactly your typical school girl, in some ways.