The 51-year-old German woman was one of the six victims who were in critical condition after the mass outrage on August 17 by the driver of a van on Barcelona's busy Las Ramblas, official sources said.
A total of 14 people have now died from the attack in Barcelona, and a woman was killed in a linked attack in nearby Cambrils.
A jihadist cell that killed 16 people in a double attack in Catalonia earlier this month managed to evade controls specifically meant to detect potential threats, Spain's interior minister said on Monday, promising to review procedures.
Earlier, Spain's Interior Minister Juan Ignacio Zoido stated that the terror cell behind Spain's deadly twin attacks cell was believed to have consisted of at least twelve persons.
Hours later, a auto sped into Cambrils, about 75 miles (120km) south of the city, hitting people before crashing into a police vehicle.More news: Shakib helps Bangladesh win Day 1 honours of Dhaka Test
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A banner as wide as a street reading "No Tinc Por", "I'm not afraid" in Catalan made its way down one of Barcelona's main streets.
Spain's King Felipe VI, Prime Minister Mariano Rajoy, and representatives of all major Spanish political parties also joined the Saturday march. The driver of the van, identified as 22-year-old Younes Abouyaaqoub, was shot dead by police after several days on the run.
Of the 12 suspects in the deadly attacks in Barcelona, Cambrils and Alcanar, two were freed last week due to a lack of evidence against them, eight have been confirmed dead and two remain in custody on charges of murder.
King Felipe VI joins the protest for peace in Barcelona.
The August 17 attack was claimed by ISIL. A further two suspects are now in prison facing charges of terrorism, while two other suspects were released.