She hasn't upset any of her students.
You don't know that. We have no idea how the majority of her students feel, since only a couple of her students (ones who were described in flattering ways) have come forward to publicly identify themselves as being characters in the book.
It's common sense that the students who were described using flattering terms would be more comfortable publicly identifying themselves, than students who were described in disparaging ways.
It seems unlikely the students referred to as "feral", or mocked for being fat and having "double chins and rotting teeth", or the girl who was raped and had her weight gain after being raped scrutinised, feel as positive about the book as the girl referred to as having beautiful almond-shaped eyes does.