The BBC said the 33-year-old was released on Monday and taken to a secure location, while her father Sergei Skripal remains in hospital.
A spokesman for the state-run National Health Service (NHS) told AFP that a press conference had been scheduled for 08:30am (0730 GMT).
There was no comment from the Metropolitan Police, which has been leading the investigation into the March 4 poisoning.
In a statement last week, staff at Salisbury hospital said of Yulia Skripal: "Her strength is growing daily and she can look forward to the day when she is well enough to leave the hospital."
Britain and its allies have blamed Russia for carrying out the attack, the first offensive use of a nerve agent in Europe since World War II, sparking a major diplomatic crisis.
(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)
Get the latest election news, live updates and election schedule for Lok Sabha Elections 2019 on ndtv.com/elections. Like us on Facebook or follow us on Twitter and Instagram for updates from each of the 543 parliamentary seats for the 2019 Indian general elections.