Police said they were continuing to investigate how Dawn Sturgess and a 45-year-old man, named by media as Charlie Rowley, came across an item contaminated with Novichok, which was developed by the Soviet military during the Cold War.
Her partner Charlie Rowley, 45, remains in a critical condition after the couple fell ill on June 30.
Basu said that Sturgess leaves behind three children, and offered thoughts and prayers for the woman's family.
Ms Sturgess, 44, who had a history of substance abuse, succumbed to the effects of the nerve agent shortly before 8.30pm on Sunday - eight days after initially falling ill at Mr Rowley's home in Amesbury, some eight miles to the north of the cathedral city of Salisbury where the Skripals fell ill.
Test samples from Sturgess and Rowley show they were exposed to Novichok "after touching a contaminated item with their hands", police said.
Russian Federation has denied any involvement in the Skripal incident. The British government blamed Russian Federation for the attack.
"I simply can not offer any guarantees", said Assistant Commissioner Neil Basu, who is leading the investigation. Yulia said that the poisoning had turned her life "upside down" and that she and her father were "lucky to have survived this assassination attempt".
More than 100 police officers were deployed to try to locate a small vial believed to have contained the nerve agent that sickened the two.
"This activity has centred on Dawn's address at John Baker House, Salisbury, Charlie's address in Muggleton Road, Amesbury, and Queen Elizabeth Gardens in Salisbury", Mr Basu said.
"Detectives are working as quickly and as diligently as possible to identify the source of the contamination, but this has not been established at this time". The hospital's medical director, Dr. Christine Blanshard, said the staff "worked tirelessly to save Dawn".
When asked about it being a murder inquiry, and whether the people involved had been targeted despite evidence suggesting it was an unfortunate occurrence, he said: "This was a deadly agent unleashed on British soil and was completely reckless, and that in itself is a reason to launch a murder inquiry".
Following the death, there are growing fears of a wider risk to public health in the region but Public Health England stressed the risk to the general public "remains low". According to Reuters, the non-profit Nuclear Threat Initiative believes that at one point, Russian Federation had stockpiled "thousands of tonnes" of the nerve agent.
"We are not in a position to say whether the nerve agent was from the same batch that the Skripals were exposed to", the Met said, adding that the investigation into the attempted murders of the Skripals were ongoing.
Skripal and his daughter were both released from the hospital this spring.
The reaction of a couple exposed to novichok in Wiltshire was "so severe" they "must have got a high dose", police have said.
Britain's interior minister Sajid Javid said earlier on Sunday that police were still working to discover how the two individuals were exposed to the nerve agent.
Britain blamed Russian Federation for the poisoning - a charge strongly denied by Moscow.
"As it stands now, the police investigation of the Skripals case is limited by political frameworks imposed by the current government".
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