The mother of a gifted young dancer who died after being hit by a train today urged every parent to be aware of the dangers of the internet and what their children may be viewing online.

Tallulah Wilson, 15, from West Hampstead, north west London, became so obsessed by the internet that she created a fantasy cocaine-taking character in order to escape reality, St Pancras Coroner's Court was told.

The inquest jury said at the end of their narrative determination: "This case has highlighted the importance of online life for young people. We all have a responsibility to gain better understanding of this. This is a particular challenge for healthcare professionals and educators."

Tallulah's mother Sarah issued a statement in which she said: "Our lives will never be the same without Tallulah. We have lost someone more precious than words could ever say - a beautiful, loving and talented shining star has been stolen from our skies."

She said that like any parent she sought to protect her daughter, seeking help from professionals at her school and in the health sector.

"Her sisters and I did everything we could to keep her safe, but she had fallen into a world of nightmares. She was in the clutches of a toxic digital world where in the final few weeks we could no longer reach her."

Mrs Wilson said she was "shocked by the ease with which Tallulah and other children can access online self-harm and suicide blogs."

She added: "Tallulah entered a world where the lines between fantasy and reality became blurred. It is every parent's worst nightmare.

"I appeal to big brands to withdraw their advertising from those sites who continue to host inappropriate self-harming and suicide-promoting blogs to stop this poison spreading.

"My family has suffered an irretrievable loss and would now appreciate some time to reflect and come to terms with a world eclipsed without Tallulah, but every parent needs to be aware of the dangers of the internet and what their children may be viewing online."

Anna Thwaites, the family's solicitor, from Hodge Jones & Allen LLP, said: "This is a tragic case. More needs to be done regarding the perils of the internet and the impact this has on our children."

Coroner Ms Mary Hassell said she would make a prevention of further deaths (PFD) report following the inquest.

During the hearing in the absence of the jury she said: "I think that I must pass on to the relevant organisation or organisations some of the learning that has clearly taken place as a direct result of Tallulah's death in terms of not simply the importance of the internet but the particular ways that it influences and the particular consequences that it has in 2014 rather than in 2013 or 2012 because it evolves so quickly.

"Whatever their (the jury's) determination is, it won't take away from that. It is the absolute minimum that I must pass on because the evolution of this is so quick that I think I would be neglecting my duty if I didn't make an attempt to pass this information on as quickly as possible."

The inquest heard that the teenager, once reportedly head-hunted by the Royal Ballet School, would go online and post pictures of herself with self-inflicted cuts.

Detective Sergeant Adrian Naylor, of British Transport Police, said last week that materials including computers, diaries and a journal had been taken from Tallulah's home as part of an investigation into her death, which occurred on October 14 2012.

He told the hearing there had been ''disturbing writings relating to self-harm and self-loathing'' in a journal that was taken from the house. One picture of self-inflicted injury on a computer had been captioned "my arm", he said.

The inquest heard that consultant psychiatrist Dr Andrew Wiener, of the Tavistock and Portman NHS Foundation Trust, had assessed the teenager as being severely depressed when he saw her in May 2012.

But by June his view was that her mood was "lifting", the court heard.

Ms Hassell, senior coroner for Inner London North, told the jury: "The last time she saw Dr Wiener on September 25 her main complaint was she felt she had no say with her mum - no say in what happened to her.

"He thought things were on track - although she still needed help and there were conflict issues, she now had mild rather than severe depression."

The jury in its determination said that Tallulah experienced low self-esteem from an early age.

"Her mother is a normal caring parent, who had conflict with her daughter," they said.

She had difficulties with some girls at school and created an online persona.

"Her mother expressed her concerns and highlighted the dangers of this activity and the possible consequences," the jury said.

During this period Tallulah started to self-harm, which was noticed by the school nurse.

"It is clear she had a rich interior life which she guarded fiercely," the jury said.

After leaving that school she attended sessions with a consultant psychiatrist who diagnosed severe clinical depression.

She was prescribed anti-depressant medication coupled with talking therapy.

She took an overdose on October 1, which resulted in an overnight hospital admission.

She was due to see a consultant psychiatrist on October 5 but did not attend this appointment, which was cancelled by her mother.

On October 8 an online account was deleted at her mother's request. "This contained inappropriate images containing self-harming behaviour," the jury said.

This resulted in conflict between Tallulah and her mother. "This site was very important to Tallulah, providing her with a medium to express herself over which she had total control," the jury said.

She did not attend the next appointment with a consultant psychiatrist, on October 12.

The next day, she met a friend she had met online. This meeting was uneventful, however it was without parental consent.

"When Tallulah's mother became aware of it, she challenged Tallulah, and this resulted in another argument."

On the day she died she was driven to dance class by her grandfather, but did not attend.

It is unclear whether she was depressed at the time that she took her own life, the jury said.

A spokeswoman for social networking site Tumblr said: " Tallulah Wilson and her family are in the thoughts of Tumblr and its employees.

"Issues of depression and self-harm are extremely challenging, particularly in online environments that encourage self-expression.

"Tumblr has policies to address the most harmful of this content, and we have systems in place to direct users to appropriate resources for getting whatever help they may need.

"We are committed to continually improving our ability to act on self-harm content, and also to keeping Tumblr a positive, supportive environment for those individuals dealing with issues of depression and self-harm."

A Samaritans spokeswoman has urged anyone who is struggling to cope to contact their helpline on 08457 909090.