Lucia Krim, 6, tried to defend herself as nanny, Yoselyn Ortega, 50, allegedly attacked her and her brother, Leo, in their New York apartment.
The Daily Mail reported sources said Lucia suffered defensive wounds as she attempted to stop the violence from Ortega, who was allegedly armed with two knives.
"The little girl tried to protect herself," the source said.
Police investigations continue into a motive, which include reports from neighbors that her behaviour changed in recent months, she lost weight and appeared to age.
She had also told family she was under the care of a psychiatrist.
The New York Post quoted a police source who said Ortega had complained of financial problems and as a result, the Krims, had given her more hours of work.
“She snapped,” said Ortega's sister, Celia.
"We don’t understand what happened to her mind.”
The 53-year-old told The New York Daily News she felt extremely guilty and to blame because she had referred Marina Krim to her sister two years ago.
“I would like to die. I would give my life for the children to come back," she said.
Detectives have been unable to interview Ortega as she remains in a medically induced coma.
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