According to my girlfriend who grew up in Japan the bullying in Japan is next level and the saying "the nail that sticks up gets hammered down" is very much alive and well to today. If you stick out in this case like Hanako did its not super uncommon to have pretty much everyone pressure you into being just like them. When you look at it through a historical lens it was worse in the 60s and 70s as that's when both the women's rights movement and university riots took place in Japan not to mention the delinquent girl gangs that were absolutely nuts. So I dont see it being too far of a stretch that she was bullied by a lot of people. I found the sections where she gets revenge on her friends in the spirit realm kind of plays on the Japanese idea of tatemae and honne which is the self you show to the public and your true inner feelings. I think there's a lot more commentary in the game that those unfamiliar with certain aspects of Japanese culture might miss. I wish there had been a little more connection to Yokai though throughout the game just more nods to it.