Last year, they returned to China to marry before buying a franchise of Sunshine Kebabs in Toowoomba to build a life together as Australian residents.
Kebab co-worker Sukhdeep Kaur Sony said Ms Cai was lovely and helpful.
"She showed me her wedding photos," she said. "They were really happy together."
Grace Cai and Calvin Zhou were killed in a car accident on Australia Day. Picture: Supplied
Ms Sony said they had planned on children after settling in Toowoomba.
"She said she wanted to buy the store then buy a house and make a future together."
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She said she was horrified to hear of the couple's sudden death.
"Normally they swapped shifts, one working at night and another opening the store … I don't know why they were together that morning but maybe it was God's plan to take them together."
Sunshine Kebabs human resources manager Muhammed Isbil said they were always happy.
Calvin Zhou and Grace Cai were building a future together when their lives were tragically cut short. Picture: Supplied
"I still can't believe it," he said. "She (Grace) was always in a happy mood, I only just talked to them on the weekend."
The couple's deaths shattered the small Toowoomba community, with the local church saying a prayer for the couple's family.
It is understood the couple's family live in China.
Forensic Crash Unit investigators yesterday examined the crash site, with the power of the collision so strong it toppled a jacaranda tree standing in front of the Allan Cunningham Motel.
Police said both cars were heading south along Ruthven St when a white car smashed into the back of the smaller hatchback.
The hatchback spun 180 degrees before hitting the tree.
The scene of a fatal car crash near the intersection of Ruthven St and Alderley St Toowoomba. Newlyweds Grace Cai and Calvin Zhou died. Pic Supplied.
The white car overturned, trapping the driver.
Several neighbours said they heard the collision, which echoed several blocks away.
The 29-year-old East Toowoomba driver of the second car was taken to Toowoomba Base Hospital with non-life threatening injuries where police yesterday interviewed him.
Investigations are continuing.