Christine Archibald, 30, would have had "no understanding of the callous cruelty that caused her death", her family said as they paid tribute to her.
She is the first named victim of the atrocity in London Bridge and Borough Market on Saturday night, which killed seven people and critically injured 21 others.
Cassie Ferguson Rowe said her brother, Tyler Ferguson, held Ms Archibald, from British Columbia, and she died in his arms.
Writing on Facebook, she said: "Last night in London my baby brother lost the love of his life on the London Bridge.
"In a split second his entire life was ripped away from him. Hearing his painful sobs on the phone while he's alone trying to deal with this tears me apart.
"I have no words. If you know Tyler, please be there for him now, and later when what happened sinks in, he's going to need us all."
Ms Archibald's family said in a statement: "We grieve the loss of our beautiful, loving daughter and sister. She had room in her heart for everyone and believed strongly that every person was to be valued and respected.
"She lived this belief, working in a shelter for the homeless until she moved to Europe to be with her fiance.
"She would have had no understanding of the callous cruelty that caused her death.
"Please honour her by making your community a better place. Volunteer your time and labour or donate to a homeless shelter. Tell them Chrissy sent you."
Canadian Prime Minister Justin Trudeau said he was "heartbroken" to learn of Ms Archibald's death.
Applauding the UK for its strength and resilience in the face of adversity, he said: "These hateful acts do not deter us; they only strengthen our resolve.
"Canadians stand united with the British people. We will continue to work together with the United Kingdom and all our allies to fight terrorism and bring perpetrators to justice."
On Sunday, Prime Minister Theresa May visited some of the 48 people taken to hospitals across the capital after the attack.
:: A British Transport Police (BTP) officer and an off-duty Metropolitan Police officer are in hospital with serious injuries but neither is believed to be in a life-threatening condition, Scotland Yard said.
The BTP officer, who was on duty, was one of the first at the scene after he responded to calls for help from the public, the force said. He suffered serious injuries when he was stabbed in the face, head and leg, wounds which BTP said are not thought to be life-threatening.
:: New Zealander Oliver Dowling is reported to have been left in a coma after being stabbed in the face, neck and stomach.
The 32-year-old, from Christchurch, is said to have had four hours of surgery for his injuries and is in an induced coma.
According to the Mirror, his sister, Freddy Dowling, said on Facebook: "Doctors are very happy with how he's come out the other side. A massive thanks to the University of London Hospital for their tireless efforts in helping my brother out."
It was reported that his girlfriend, Marie Bondeville, was also injured.
* Sunday Express business editor Geoff Ho was left in intensive care after being stabbed in the throat when he tried to help a wounded bouncer.
Mr Ho was filmed being led away from the scene by a policeman, clutching his neck and with his shirt off.
According to the Mirror, he wrote on Facebook: "Don't know whether it was stupid or noble to jump in and break up the fight outside the Southwark Tavern, but two a***s trying to do over the lone bouncer on the door isn't happening on my watch."
Friend Isabelle Oderberg tweeted: "We have found Geoff. He is in intensive care." She told Melbourne newspaper The Age: "He is actually a martial artist and I wouldn't be surprised if he would have stood up and been counted because he's just that type of person."
* Two Australians were stabbed in the neck while Prime Minister Malcolm Turnbull said the government had "very real concerns" about another two citizens who may have been caught up in the attacks. Candice Hedge is recovering in St Thomas' Hospital, while Andrew Morrison received stitches for a wound and was on his way home to Australia.
* A French citizen died in the attacks and seven were taken to hospital, four of whom were in a critical state, foreign affairs minister Jean-Yves Le Drian said.
Another French national is missing, he added.
Newspaper Ouest-France reported the victim was from St Malo, Brittany, and worked in a bar in the London Bridge area.