didn't want others to use honorifics to her because of her trauma from the previous 5 timelines that she was forced in automode, the automodeMariaBell was a haughty, brazen, arrogant and nasty villainess who treated others like craps and made everyone speak to her in honorifics. In the childhood arc, the novel made it clear that Grey's family (a fallen earl family) was so poor, Grey was 13 (or so i can't remember clearly) at that time, if he lost the job, he would have suffered so bad that his personality twisted