Federica Boscolo-Gnolo, 32, pleaded guilty to the manslaughter of little Farah, whose body has never been found.
A court heard the victim was born on November 22, 2014 in Chioggia, near Venice, and is thought to have been killed on January 25 last year after her mum brought her to London for medical treatment for a minor eye condition.
But Boscolo-Gnolo told cops her daughter had been abducted from Lily Hotel in Earls Court on the same day.
Police eventually arrested the Italian national on January 29 after carrying out extensive searches for Farah across London.
Despite combing through the hotel, a local rubbish dump and other locations, the baby”s body has never been found.
Boscolo-Gnolo, of no fixed address, stood at the dock today (February 22), flanked by mental health workers, at the Old Bailey.
She was due to stand trial for murder, but when the manslaughter charge was put to her today, she answered via a translator: “Not guilty to murder, but guilty to manslaughter by reason of diminished responsibility.”
Judge Nicholas Hilliard QC, the Recorder of London, adjourned her sentencing until April 8.
The defendant is likely to be made subject to a secure hospital order under the Mental Health Act.
Detective Inspector Jamie Stevenson said: “This is a tragic case for all involved and Boscolo-Gnolo will have to live with her actions for the rest of her life.
“Farah had already been rejected by her father, who chose not to be a part of her life, she was then victim to the one person who should have protected her most.
“Boscolo-Gnolo”s parents now have to come to terms with losing their daughter, and their granddaughter who they were just getting to know.”