The young girl shot dead on Sunday with her father, a convicted crack dealer, had been under the protection of social services.
Birmingham City Council moved Toni-Ann Byfield, aged seven, from foster parents in the Midlands to live in London shortly before she was murdered at her father's bedsit.
Child protection officers have begun an inquiry to find out why she was able to spend the weekend with her father - the victim of a previous shooting - at his one-bedroom flat in Kensal Green, north-west London. He was barred from having her to stay under the terms of a care order.
Toni-Ann was shot once in the back as she fled from the killer of her father, Bertram Byfield, 41, early on Sunday. The girl, who police believe was killed to prevent her from identifying the gunman, was supposed to be living with a woman described as an aunt, but who may not be related. Police were continuing to question a 23-year-old man about the double murder last night.
Toni-Ann's mother, Christine Richards, was traced yesterday in Jamaica, where she has two sons, Jermaine, 13, and Kieron, 10, and told of her daughter's death.
Speaking from her home in St Andrew, she said: "If I hadn't sent my daughter to UK, she would still be alive.
"The last time I spoke to her was a few weeks ago and she said to me 'Mummy I want to see you'. I'm supposed to be seeing her in December.
"I was shocked when I heard, my first reaction was to blame myself. I know that I should have flown to get her back before."
She added: "I know her father loves his daughter so I thought she would be fine in England. He was a good father, he loved her, I wanted her to be with him. I would rather they end up dead together than apart.
"My sons are taking it real bad. Jermaine took a knife to cut his own throat. I have to be strong and not cry in front of them."
She said she was preparing to travel to Britain for the funeral.
The shooting, which is being linked to a dispute between crack cocaine dealers, has caused public revulsion and highlighted the rise in gun crime. There have been more than 100 shootings in London since January linked to drugs.
Toni-Ann's murder has raised fresh questions about the care of juveniles and comes less than a year after the inquiry into the murder of eight-year-old Victoria Climbié recommended better co-operation and vigilance by agencies dealing with children.
Toni-Ann arrived from Jamaica in June 2000 and settled in Birmingham. The city council's social services department was alerted in November last year that the girl was at risk.
She was removed from her carers and placed with a foster family after the council obtained a interim care order, which gives them legal guardianship of the child. Such orders are issued in cases where the child is considered to be at risk.
Last month, the girl was sent to north London to live in the borough of Brent under the care of a woman described by Birmingham City Council as an aunt. Social workers from Birmingham visited her several times and Toni-Ann was due to start at a new school this week.
However, when questioned by police, the woman was unable to tell them how she was related to Toni-Ann.
Under the court order, the girl was allowed to see her father, but is not thought to have been given permission to stay with him last weekend.
Andrew Sewell, the headteacher of Slade primary school in Birmingham, where Toni-Ann had been a pupil since November last year, told the children about her murder at assembly yesterday.
He said later: "She was a bright, lively girl who made friends easily. Although she was at Slade for a relatively short time, she will be sadly missed by the staff and pupils."
Toni-Ann's father, a British national, was born in Beckenham, south-east London but grew up in Jamaica.
He returned to live in Britain 11 years ago and in 1997, shortly after Toni-Ann was born, was jailed for nine years for supplying crack cocaine. He was released from jail in October 2001.
On 29 January last year he was shot six times in what police have described as a "domestic" rather than a gang-related incident.
Robert Grant, 23, was acquitted of attempted murder at the Old Bailey in October last year.