Aww, even though she thinks he's a perv, she still wants him to avoid misusing the language just in case he's not one. Her efforts may be misguided but her intentions are noble.
That last page, though: I get why a highschooler who likes ESL may be seen as a weirdo, but what's so weird about him liking melons? Is it childish to like them or something? I haven't eaten any myself, so I wouldn't know.