Marcelle O'Brien was sent to a home in Pinjarra, western Australia, run by the Fairbridge Society, at the age of four.
The then-Queen, wife of George VI, later intervened to ask whether she could return to the UK to be adopted.
But Fairbridge said it would not be in her "best interests", the Independent Inquiry into Child Sexual Abuse heard.
Mrs O'Brien said she suffered "mental cruelty" and "sadistic" treatment at the home where she was forced to do "slave labour".
She was molested by her school's deputy principal and caned, the hearing was told.