Lorella Querel, 73, was asleep in her third-floor apartment in Muggia, a town near Trieste, when the landslide hit, Today.it reported.
Two sisters also died after torrential rains and floods hit the town of Maremma in southern Tuscany on Tuesday.
The two women, identified as Marisa Carletti, 69, and her sister Graziella, 65, from Manciano, were swept away in their car by the flood after the Elsa river burst its banks due to torrential rain between Albinia and Manciano.
Their vehicle was discovered in a field around 60-70 metres from the road where they had been travelling, surrounded by mud, Tgcom24 reported.
The bodies were recovered by divers who are now looking for any other cars which may have been swept away by the floods.
Residents in the nearby town of Orbetello were alerted via text message, asking them to move to the upper floors of their houses.
Families living in the high-risk areas of Polverosa, Aunti, Alberone and Priorato have been evacuated. Firefighters have also rescued nine people with hypothermia.
A 57-year-old man also died when the northern city of Genoa was hit by torrential rain late on Thursday night, causing the river Bisagno to breaks its banks and killing.
On Monday, Italian Prime Minister Matteo Renzi announced that €2 billion will be given to build safety measures in the flood-hit city.
The announcement follows an outcry at the government’s failure to build flood safety measures in the city since the last serious flood in 2011, when seven people, including two children, lost their lives.
The €35 million set aside for the works was never spent due to legal wrangling and bureaucracy.
Meanwhile, volunteers known as "mud angels" have been working since Friday to clear up the mud in the flood-hit city.