Police and social services missed a number of chances to help 13-year-old Lucy McHugh in the months before she was murdered, says a report.
Stephen Nicholson, 25, was sentenced in July 2019 to a minimum of 33 years in prison for the brutal killing and rape of the teenager.
Social services did not do enough to act on concerns raised by Lucy's school that she was being sexually exploited by an older boyfriend, according to the report by Southampton Safeguarding Children Partnership.
Lead reviewer Moira Murray said authorities decided there was "no foundation" to the concerns because of "assurances" given by Lucy's mother.
Ms Murray said a lack of information sharing between police, the school and children's social care was a "missed opportunity" and meant Lucy's case was not treated as one of child protection.
Nicholson - described as a "predatory paedophile" by police - lured Lucy to woodland at Southampton Sports Centre on 25 July 2018 and stabbed her 27 times.
His trial heard he murdered Lucy after she threatened to reveal he had been sexually abusing her.
Lucy's mother, Stacey White, was "defensive, controlling, aggressive and intimidating", says the review, and should not have been allowed to influence the judgement of the children's social care team.
Ms Murray wrote: "Such behaviour should not be allowed to detract from the need to focus on the safety and wellbeing of children.
"Thus, professionals need to be aware of disguised compliance, be resilient when faced with hostility, and confident in understanding when to escalate their concerns."
Police and social services also failed to take into account Nicholson's previous convictions, says the review.
These included theft, battery, criminal damage and domestic violence.
Rob Henderson, executive director for wellbeing (children and learning) at Southampton City Council, said: "We remain deeply saddened by this tragic case, and on behalf of the council I would like to apologise to the victim's family, friends, and all who knew her, for the council's shortcomings identified in the report.
"We have already made changes in a number of the areas highlighted."
He said these included "quicker and more effective" information sharing and speeding up child protection referrals.
Superintendent Kelly Whiting, of Hampshire Police, said: "We have been working closely with our partners to identify improvements following this tragic death.
"We have taken action to improve the way referrals are made to our partners and have set up a multi-agency police protection safeguarding notification scrutiny panel."
