The woman who fell into the Thames during last month's London terror attack has died, taking the death toll from the day to six.

Andreea Cristea, a Romanian national who had been visiting London at the time of the attack, died in hospital after her life support was switched off on Thursday, police said.

Ms Cristea fell into the River Thames from Westminster Bridge after being driven at by Khalid Masood who ploughed a rented car into pedestrians and stabbed a policeman to death before being shot dead on March 22.

Her family, together with her partner Andrei Burnaz, remembered Ms Cristea as "a wonderful daughter, sister, partner, dedicated friend and the most unique and life loving person you can imagine".

"After fighting for her life for over two weeks, our beloved and irreplaceable Andreea...was cruelly and brutally ripped away from our lives in the most heartless and spiritless way," they said in a statement.

"Andreea is now unfortunately not able to have part of the money that was raised for her recovery, so we would like to donate it to charity. She would not have it any other way.

"There are no words to even begin to describe the crushing pain and emptiness that is left in our hearts."

The grieving family thanked the "unimaginable efforts and never-ending dedication" of the doctors and medical staff who treated Ms Cristea, and the police and government officials who supported them.

"Their kindness and empathy are beyond compare," they said.

"Our hearts and love go out to our two Family Liaison Officers, Detective Sergeants Tony De-Wilde and Geraint Jones, who stood beside us every single step of the way. You were our lifeline and we will never be able to thank you enough."

Reuters, Fairfax Media