Catherine Wynter's body was found by her mother on Tuesday at Borehamwood house
An 18-year-old man has been charged with the murder of a teenager who was stabbed to death while babysitting her young niece and nephew.
Catherine Wynter, 19, had been looking after her sister's children on Boxing Day. Her body was found by her mother at 8am on Tuesday.
Tony Bushby, of Digswell Close, Borehamwood, Hertfordshire, will appear at Hatfield magistrates court on Saturday, Hertfordshire police said.
Wynter was last heard from at about 7.30pm on Boxing Day, police said.
The children, aged three and four, were in the house in Beech Drive, Borehamwood, at the time of the murder but were not injured. It is believed they could hold vital clues about the incident.
A postmortem examination confirmed that Wynter, who lived elsewhere in Borehamwood, died as a result of stab injuries.
On Wednesday night, a 26-year-old man from Islington, north London was released without charge after being held in connection with the killing.
Police said both men were known to Wynter and her sister, but were not direct relatives.
Detective Inspector Carl Foster, from the Bedfordshire and Hertfordshire major crime unit, said: "Whilst a charge has been made, a team of detectives continue to work on the case.
"As part of our ongoing investigations, extensive searches by specialist officers have been carried out in the area surrounding Leeming Road and Gateshead Road to locate a black binbag. It is believed there are clothes in this bag which we are keen to trace.
"I would like to appeal to people in Borehamwood for help in tracing this binbag. If you have seen a bag in the area which you have found to be in an unusual place or believe there is something suspicious about it please call Hertfordshire police on 101 or Crimestoppers anonymously on 0800 555 111."