A teenage boy has been sentenced to a minimum of 13 years for the murder of 12-year-old Ava White.
The 15-year-old was given a life sentence on Monday for the fatal stabbing, which happened in Liverpool city centre on November 25 last year.
Addressing Liverpool Crown Court, Ava's mother Leanne said: "My beloved Ava dies all over again every morning I wake up.
"My Ava dies again every moment she is not with us for the rest of our lives."
The defendant, appearing via videolink, covered his face with his hand as Ms White and her older daughter Mia, 18, tearfully addressed the court, where more than 20 of Ava's family and friends were in the public gallery.
Mia said: "I am a shadow of my former big, loving sister to Ava."
She said she was anxious to walk past groups of youths in the street in case they were carrying knives and now hoped to change other young people's minds about using knives.
The defendant, who was 14 at the time of Ava's death, stabbed the schoolgirl in the neck following a row over a Snapchat video.
He claimed he accidentally stabbed her in self defence but a jury convicted him of murder following a two-week trial in May.
The court heard the boy, who has attention deficit hyperactivity disorder (ADHD) and attended a special school, had previously been subject to a community resolution notice after hitting a PCSO last July.
At the time of Ava's death the boy was charged with other offences which have not yet been resolved, the court was told, and had come to the attention of the authorities because of concerns he was being exploited by older, more criminally sophisticated people.
Nick Johnson QC, defending, said the defendant was carrying the knife because he had previously been a victim of crime.
Referring to a pre-sentence report on the defendant, Mr Johnson said: "One of the things that shines out is the suggestion that as part of his background he had been desensitised to violence, and that is not as a perpetrator of violence."
The court heard Ava and her friends became involved in an argument with the defendant and three of his friends after the boys recorded Snapchat videos of the group.
Friends of Ava said the boy "grinned" after stabbing her in School Lane, just after 8.30pm.
The court heard that after Ava was struck in the neck the defendant ran away, discarded his knife and took off his coat, which was later found in a wheelie bin.
CCTV showed him and his friends in a shop where the defendant took a selfie and the group bought butter, which he said was for crumpets.
He then went to a friend's home and when his mother contacted him because police wanted to speak to him, he told her he was playing a computer game.
After he was arrested, just after 10.30pm, he initially told police he had not been in the city centre but in later interviews blamed another boy for the stabbing.
Applications from the media for reporting restrictions to be lifted on the defendant's identity were refused by the judge.