Jessica Scatterson took her own life at home in Warrington, Cheshire, at 3.45am on April 22, 2017.
An inquest into her death heard her social media activity had been ramped up to 'intense' levels which led her to be 'emotionally overwhelmed' before her suicide.
Drawings and notes referencing death and suicide were found in her room days after she passed. The notes included the name of an alleged bully.
Nasty messages between the girl and her friends in the days leading up to her death were discovered on her iPad, the inquest heard.
The hearing was told that Jessica's friends knew she had previously self-harmed, but never told her parents or teachers at Penketh High School.
A police inquiry revealed there had been an incident 'relating to Jessica being bullied at school' in April 2016.
Inspector Hannah Friend said Jessica had come home with scratches to her face and a swollen eye after arguing with another girl. The matter was reported to the police but it was unclear who started the fight so no action was taken.
When quizzed by police, Jessica's friends denied she was bullied and said she 'gave as good as she got'.
Senior Coroner for Cheshire, Alan Moore, said: 'The level and the intensity of her activity on social media platforms… cannot have failed to have influenced her intentions.'
The British government has warned social media giants such as Facebook and Instagram they'll be hit with multi-million pound fines if they fail to rid their platforms of harmful content.
UK ministers are planning to launch a tech regulator that can impose the penalties on the firms for failing to delete posts that promote suicide or self harm.