The counsellor had informed my stepdaughter that a hatred of one’s breasts could be an indicator of a non-binary, or transgender male identity
Oh god damn these idiots to hell! What qualifications does this shitforbrains 'counsellor' have? And the school -- beyond disgraceful.
I hated my breasts at that age, and hid them as much as I could, for the same totally obvious reason as your stepdaughter and millions of other girls -- sexual harassment by men. Much exacerbated these days by the porn-soaked culture children grow up in, no matter how much their parents try to protect them.
I'm so sorry your stepdaughter, and all your family, are being put through this totally unnecessary stress and pain, Du. Bad enough when a child is ill, but when a child is mistreated by adults -- unbearable. Love and best wishes to you all, and I hope both your little daughter and your stepdaughter recover fully. 