The 35-year-old woman was allegedly chanting verses of the Koran as her daughter's disembowelled corpse lay next to her in the home in Clapton, East London.
The mother, who is understood to have two teenage children of 14 and 16, has since been sectioned under the Mental Health Act and is in a secure unit as police yesterday continued to guard the third-floor premises on the estate.
The gruesome scene was discovered by the girl's father, Jerome Negney, when he arrived home to the flat on Thursday to find his partner clutching a kitchen knife.
Another neighbour, who lives in the downstairs flat and asked not to be named, said: 'I was feeding my daughter her lunch at about 3pm and suddenly heard horrific screaming. It is shocking and so upsetting.'
A post-mortem examination will take place on Saturday at Poplar mortuary in east London.
The Metropolitan Police's Child Abuse Investigation Command is leading the murder inquiry. They are not believed to be looking for anybody else.
Yesterday another shocked resident, a mum in her 30s, said the mother always wore a black headscarf with a veil.
She added: 'Usually you could only see her eyes.
'I often heard shouting coming from the flat as she and a man argued.
'Their quarrels would become very heated.'