A teenager has been convicted of murdering a girl by stabbing her at a 16th birthday party last April.
Martins-Paes kept a hit list of people she hated and wanted dead
Beatriz Martins-Paes killed Charlotte Polius, 15, when she plunged a knife into her on the dance floor at a party in east London over a petty matter.
Martins-Paes, now 18, of Brentwood Essex, had admitted manslaughter at the Old Bailey, but denied murder. She was remanded until 20 March for sentencing.
A prosecutor said the case exposed "a sinister development in society".
The court earlier heard how the defendant asked Charlotte: "Do you want me to shank (stab) you?" before drawing one of two knives, which she regularly carried with her, from a bag.
She then stabbed Charlotte, removed the knife from her chest and placed it back in her bag before trying to leave the party in Ilford.
Martin-Paes, who was 17 at the time, had told the jury: "I didn't mean to stab her at all.
"None of that was supposed to happen. I didn't think of the consequences."
But it emerged she had a hit list of people she hated, including a teacher, the court heard.
On it, she wrote: "The real world is horrible sometimes. You have to be violent. Get what you want right now. I want the following stabbed. I wish violent death on them."
The murder had followed a feud between Martin-Paes and another teenage girl a month earlier, said Aftab Jafferjee, prosecuting.
Charlotte, of Stratford, east London, had been present but not involved.
However the defendant was determined to continue the feud at any cost and Charlotte became the unwitting victim.
Mr Jafferjee told the jury the trial "exposed a new and sinister development in our urban society - the carrying of knives by teenage girls".
In a statement made following the conviction, Linford Polius, Charlotte's father, said: "Our daughter Charlotte was taken away from us over something that seems so trivial.
"Charlotte had everything going for her and for this reason I, as her devoted father, will never ever forget or be able to forgive."