She had never been happy about Sophie seeing Weatherston, and could now cite a list of warning signs that had prompted her unease.
"I didn't like the way he treated her and the things he said to her, but I did not see her as abused," she said.
There had been subtle - and far from subtle - signs of an unhealthy relationship - Weatherston's efforts to control Sophie's movements and activities, telling her she was stupid, that her ears stuck out, that her eyes were too close together, that her hair was horrible that she needed to lose weight.
"Sophie was a strong person, but she believed him," Mrs Elliott said.
"Everything she did - her work, her studies, her friendships - became less important to her than her relationship with Weatherston. That wasn't like her."
Another friend said in the video that Sophie had known she should have been treated better, but she had kept returning to Weatherston, believing she could "fix it".
It was like an addiction, she said. Sophie had developed tunnel vision.
"She didn't look happy any more. She cried a lot. It was almost like crushing her spirit."
Mrs Elliott likened the abuse to brainwashing; she could not understand why Sophie had believed what Weatherston told her, but the red flags, including an extraordinary lack of empathy, were obvious now.
It was not until she saw the Women's Refuge definition of abuse that she fully realised just how abused her daughter had been.
She now knew that psychological abuse could be as lethal as physical abuse.
After Weatherston's trial and sentencing to life, with 18 years non-parole, she put together a presentation and taken it to four girls' schools in Dunedin.
Five years later, she was still delivering it, and would keep talking for as long as anyone wanted her to.