The father of a teenager who killed herself by standing in front of a train said her mental health worsened after she was raped a few weeks before.
Miss Miller had made attempts on her life before, the inquest heard
Mark Miller was speaking after an inquest into the death of Kay Miller, 14, on the railway last August.
The Cardiff inquest jury decided the schoolgirl took her life while the balance of her mind was disturbed.
Mr Miller, 46, said he hoped his daughter had been able to do some good before she died.
The inquest heard that although the teenager had suffered from anorexia and depression for years, that illness was not the main trigger for her death.
Speaking after the verdict, Mt Miller agreed with his daughter's psychiatrist, who told the court while his daughter had made progress with her other health problems the rape "pulled the trigger" in her mind.
Mr Miller said: "I think the rape was the main trigger.
"She was improving and coming on really well, but after the rape there was a marked downward spiral in her condition, her medication had to be increased.
"Whereas before she was having more good days than bad, she went the opposite.
He added: "It was a shock to us all how quickly it happened.
The inquest heard that as well as anorexia, the Cardiff schoolgirl had a personality disorder for six years before she killed herself near Heath High Level railway station in Llanishen.
Jurors were told that she ran away crying on the evening she died after a row when an alleged bully had been confronted by her stepbrother.
The teenager then walked in front of the train travelling at 40mph between Heath High Level and Llanishen stations in Cardiff.
A photograph, taken from the train's cab camera, showed Miss Miller facing the oncoming train, her hands by her sides, moments before she was hit. A witness later described the image as "haunting".
South Wales Crown Prosecution Service (CPS) confirmed the rape investigation was discontinued following Miss Miller's death.
Her father said: "I was annoyed when they first said they'd dropped the case, but they explained her mental health problems would have been aired in court and Kay could have been made out to be someone who fantasised or played on her illness.
"It was the right decision seeing as Kay was no longer around to defend herself against what he might say. He can't do Kay any harm now."
Coroner Mary Hassell, summing up the evidence, said Miss Miller had been described as happy, bright and articulate, but troubled.
"One description of her was she was deep," she said.
The coroner also referred to how both her psychiatrist and her stepfather referred to the teenager's depression as a "black monster" inside her.
Miss Miller received a lot of psychiatric assistance and was prescribed a number of medicines, said the coroner.
"Kay had a long history of self harm and she told her family 'just let me die'," she said.
Kay Miller's father said after the inquest he hoped his daughter had been able to do some good before her death.
"She made a few speeches to professional bodies about mental illness which I hope they can take on board so other families don't have to go through a tragic loss like we have," he said.