Cornelia Rau was expelled from a secretive Sydney cult after being humiliated in a cruel shaming ceremony.
She joined other members of the cult on a trip to Melbourne to stage a social get-together and concert in October 1998.
Witnesses said she was humiliated, "demonised" and expelled.
The activities of Kenja - run by millionaire guru Ken Dyers - are under investigation by the police.
The Surry Hills-based cult has refused to comment.
"Cornelia's part in the show was with two other girls. They were to perform a song and some spoken parts," a witness to her humiliation told The Daily Telegraph.
"Up until then she was one of the acknowledged few, in favour."
That soon changed.
"Dyers saw that she wasn't coming across as terribly alive and told her in front of everyone that she was pulling down the energy of the trio and accused her of dragging them down," he said.
"He said she had very strong evil entities - ghosts."
Other witnesses who attended the gathering at a Melbourne hotel in October, 1998, remembered the performance, and Cornelia's humiliation.
It involved Kenja members singing songs, dancing and engaging in other artistic efforts.
One witness said humiliation was a common Kenja technique - "building them up and tearing them down".
"Going back to the hotel on the bus she was very vague, staring into space, disturbed," another former member said.
That was the last time most members saw her.
"That was it. She was cut out of Kenja - vilified and demonised as having evil entities that would destroy Kenja," a witness said.
"This had happened before and has happened since and we're told not to talk to the person, to keep away from them and never speak to them again."
The Federal Government has launched an inquiry into how Cornelia ended up in Baxter detention centre after being mistaken for an illegal immigrant.
A public rally in Sydney yesterday heard demands for the inquiry to be held publicly.
Greens senator Lee Rhiannon said Cornelia's experience was chilling: "We can't imagine what Cornelia has gone through and we are not going to know with this limited government inquiry."