The Romanian woman who fell from Westminster Bridge into the River Thames during the terrorist attack was due to receive a marriage proposal later that day.
Andreea Cristea, 29, was visiting London with her boyfriend Andrei Burnaz for his birthday when she was ploughed into by a jihadist driving a 4x4 on the bridge.
Footage of the atrocity on Thursday appears to show the architect falling from the bridge as the attacker ploughed a car through pedestrians in London.
It is not known whether she fell or jumped, but Romanian ambassador Dan Mihalache said he thought the car mounted the pavement and hit Mr Burnaz first.
He believes this then pushed Miss Cristea into the Thames. He told the BBC: "It is quite a dramatic story because they were two people that were tourists.
"They were coming to London to celebrate their birthday. He intended to ask her for marriage in the same day and this was unfortunately their destiny.
"It is quite a miracle that she could survive this very complicated experience because she was practically thrown to the Thames."
Miraculously, Miss Cristea was plucked to safety by a passing cruise ship.
She was taken to hospital and had surgery last night to remove a blood clot on her brain. The ambassador said Miss Cristea was "stable, but in a good direction".
Although she has shown signs of slight improvement, she remains in a critical condition under observation owing to problems with her lungs.
British-born Khalid Masood, 52, killed four and injured 50 people after mowing down pedestrians on the bridge before stabbing police officer PC Keith Palmer.
Miss Cristea and her boyfriend were said to have just visited Westminster Abbey and the London Eye before they were injured in the attack.
Footage captured her falling into the river. The staff, on a City Cruises boat, could not get her out of the water but a nearby fire service boat came to her rescue.
A witness told the Sun: "They tried to fish her out with a pole but she was not responding. Then a rescue boat came and took her out."
The captain stopped the boat and held her out of the water to stop her being carried away by the current before emergency services took over, the spokesman said.
Paramedics treated Miss Cristea at a pier and she was taken to hospital. She had surgery overnight which was described as "successful".
Mr Burnaz, whose birthday is today, suffered a knee injury but has been discharged from hospital.
She had been due to marry Mr Burnaz this spring and they had come for a holiday from their home in the Romanian city of Constanta.
City Cruises has confirmed a crew assisted fire services in the rescue operation.
Kyle Haughton, managing director at the firm, said: "City Cruises" Millennium Diamond was in the area of the incident at the time and worked alongside London's emergency services to support in the rescue efforts of a woman in the water.
"Once alerted by people on the bridge, the ship's Captain reacted fast on spotting her, he halted the boat in order to hold her out of the water and stop her from being carried any further by the current.
"The emergency services were called immediately and arrived within minutes to take over the rescue operation.
"On behalf of City Cruises, our thoughts are with the families of the victims of this incident."
One witness, bus driver Michael Adamou, 25, said he believed at least one woman had jumped into the Thames to escape.
"The first thing I saw was the two people laying lifeless on the floor," he said.
"I heard one guy come running behind me shouting his wife had jumped into the river to avoid getting knocked down."
The Port of London Authority said on Wednesday that a female member of the public was recovered from the river, injured but alive.
The couple were due to meet a friend, retired surveyor Patrick Tracey, 64, from Derby, at the London Eye.
Mr Tracey said: "I realised that my friends were over at Westminster Abbey coming to meet me and I got a telephone call from him.
"But I couldn't hear anything because of the din... That was when he said he had lost Andreea. I don't know how seriously hurt she is. He was injured on his leg. I imagine it's the vehicle."
Paul Ciocoiu, a spokesman for the Ministry of Foreign Affairs in Romania, told Digi 24 TV yesterday: "According to information we have, she would be the pedestrian hit by a car and thrown into the Thames and then recovered. Ministry contacted the family.
"We do not know when the family arrived in Britain. If the family require consular assistance, of course, the ministry provides help punctually.'