A judge has ordered a teenager to delete her Facebook accounts after she sent harmful messages to a schoolgirl who later died in a suspected suicide.

The teen, who has statutory name suppression because of her age, has met with the victim's family and apologised.

The dead girl's mother says she has forgiven the teenager and has only pity for her.

The teenager is one of the youngest people to be charged under the Harmful Digital Communications Act since it came into effect in mid-2015.

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She had put harmful posts on Facebook about 13-year-old Villa Maria College student Chelsea O'Byrne, who died in a suspected suicide in August last year.

Chelsea suffered from mental health issues, a relative had recently died, and she was receiving counselling in the months leading up to her death.

The teenager sent the messages several days before Chelsea's death.

Chelsea's mother said meeting the teenager at a family group conference was a healing experience, and not what she expected.

"It's helped me move forward," she said.

"I just felt sorry for her. All the people there for her were professionals, not her loved ones. It's pretty sad.

"At the end of the day it's given me closure, I wasn't expecting it, but it did. I wasn't expecting to forgive her, but forgiving sets you free."

The teenager, understood to be 16 at the time of offending, appeared in the Christchurch Youth Court on Tuesday to discuss her progress with the judge.

She had admitted one count of causing harm by posting a digital communication as well as two unrelated charges of assault and one of threatening to kill. One charge of assaulting her mother was withdrawn on Tuesday.

Judge Jane McMeeken ordered the youth, who has been in Oranga Tamariki care, to delete her Facebook accounts. The teen has started her 40 hours of community work and must attend support programmes for drug and alcohol abuse.

"You can't change what has happened in the past, but you can make the rest of your life positive," Judge McMeeken told the youth.

Chelsea's mother said police told her the offender was the youngest person charged under the Harmful Digital Communications Act.

The Act came into force in July 2015, allowing civil and criminal action to be taken against harmful online behaviour.

Eighty-four people were convicted of offences under the act to the end of 2017. Of those, 12 were aged 19 or younger.

Chelsea's mother said there was little support for families who had lost their loved ones to suicide. She has reached out to fellow bereaved mothers to start a community of support.

Netsafe chief executive Martin Cocker said the case was "a reminder that these online disputes and abuse and harassment can lead to real harm and irreversible consequences".

He said if users were not concerned about breaking the law, they should be concerned about the real harm of their public posts.

"People need to know that their actions do have consequences and they can be severe," he said.

Christchurch-based registered psychotherapist James Driver said the difference between social media abuse and verbal or physical disputes was people were less mindful of the harm they could cause online.

"The difference of this is the inescapability of it. It follows them home or onto Facebook or Instagram or whatever, they can't get away from it.

"It can create a greater sense of hopelessness."

The coroner is yet to hold an inquest into Chelsea's death.

WHERE TO GET HELP

Lifeline: 0800 543 354 - Provides 24 hour telephone counselling

Youthline: 0800 376 633 or free text 234 - Provides 24 hour telephone and text counselling services for young people

Samaritans: 0800 726 666 - Provides 24 hour telephone counselling.

Tautoko: 0508 828 865 - provides support, information and resources to people at risk of suicide, and their family, whānau and friends.

Whatsup: 0800 942 8787 (noon to 11pm)

Kidsline: 0800 543 754 (4pm - 6pm weekdays)

The Lowdown: thelowdown.co.nz - website for young people ages 12 to 19.

National Depression Initiative - depression.org.nz (for adults), 0800 111 757 - 24 hour service

If it is an emergency or you feel you or someone you know is at risk, please call 111

For information about suicide prevention, see www.mentalhealth.org.nz/suicideprevention.