Elizabeth Edwards, who is understood to have been from Edinburgh originally, was found dead in her bed in April this year, after being “repeatedly” stabbed by the 15-year-old.
Police discovered the popular school dinner lady surrounded by blood stains on the wall, floor and bedding of her home in Spalding, Lincolnshire.
Her daughter, Katie, 13, lay deceased in the next room after the teen also attacked her.
Yesterday, ahead of the start of an eight-day trial at Nottingham Crown Court, the boy pleaded guilty to murdering the pair.
His alleged accomplice, a 15-year-old girl, pleaded guilty to manslaughter but denies murder.
The court heard that she listened to the mother and daughter struggling while the male carried out the attacks.
Both teenagers, who cannot be identified for legal reasons, are alleged to have planned the killings before carrying them out at the house in Dawson Avenue on April 15.
A group of Ms Edwards’ family gathered in the court room to hear the details.
Opening the case for the prosecution, Peter Joyce QC said of the victims: “They were both stabbed through the throat in their beds at their home.”
The jury heard how the boy had four knives in a backpack as he entered the house, including a large black-handled kitchen knife.
Discussing Ms Edwards, 49, Mr Joyce said a pathologist “found eight sharp force injuries of which five were on her hands, which suggested she may have been trying to fend off her killer”.
Ms Edwards had also been stabbed once in the shoulder, and twice – fatally – in the neck.
The Crown’s QC added: “The injuries would not have been instantly fatal and there is evidence that Elizabeth Edwards survived for a short time.” .
Her daughter was found lying on a mattress in her bedroom with two stab wounds to her neck and a pillow over her face.
Mr Joyce added that a post-mortem concluded that Katie died from “bleeding – haemorrhage – and smothering”.
Before leaving the property, the boy had covered Katie’s face with a sheet.
The bodies were found by police who broke down the door to the address about 36 hours after the murders. Inside the house, officers discovered a large kitchen knife in one of the bedrooms, which the prosecution has said was the weapon used in both the killings.
Both teenagers were arrested shortly after officers made the discovery.
49-year-old Elizabeth Edwards was a member of St Paul’s Church inSpalding.
The trial continues.