Financial consultant Bhavita Patel, 33, died on Monday night, 10 days after the incident in the city's centre.
Police allege Dimitrious Gargasoulas, 26, drove his car into pedestrians in Bourke St Mall, killing six people and injuring 36 others.
"My parents and I are broken," Ms Patel's brother, Mitesh, told the Herald Sun newspaper on Wednesday.
"But we all appreciate the love we're getting from people."
Four of those killed have been named as three-month-old Zachary Bryant, Thalia Hakin, 10, Matthew Si, 33, and Jess Mudie, 22. Another victim, a 25-year-old man, has not been identified.
Police said the incident was not terror-related.
Mr Patel told the newspaper his sister had a successful career with the accountancy firm Deloitte.
He said he spoke to her regularly, including on the day of the incident.
"She was cherished by so many people and we have been overwhelmed by the love and support from family and friends," Mr Patel said.
Victorian Premier Daniel Andrews said grave concerns were held for one of the seven survivors still in hospital.
It came as a makeshift memorial in Bourke St was dismantled on Tuesday, with volunteers carefully removing cards, children's toys and bouquets of flowers.
"It's time to gather up these tributes," said Melbourne's Lord Mayor Robert Doyle. "It's a monument to life, not a monument to tragedy."
The city said it would scatter the flowers at a memorial garden for victims of crime near the state's parliament.
Mr Gargasoulas will face a court hearing in August on multiple charges of murder.
The sixth victim of a motorist who allegedly deliberately hit pedestrians in Melbourne has been identified.