I'll give the girl berating MC the benefit of the doubt that she doesn't know that this is the student who was in a coma due to defeating a high-class enemy, but if she doesn't know then either she isn't high enough to know the on-goings in the school or the school must've put a hold on that info.
Aside from that, I don't know why it's showing that this two will have an animosity between them, since in his previous life the MC enjoys playing as the protagonist and the protagonist doesn't hate the mob character MC was born into.