Now she's pushing for the Alberta government to quickly finish twinning the highway to prevent more people from dying. It's what her son would have wanted her to do, Hollowell said Tuesday from her home in Niagara Falls, Ont.
"It seems like these people in higher places just don't get it," she said. "I don't think it gets any worse than this collision."
Her son Daniel Sennett and his daughter, 11-year-old Faith, of Airdrie, Alta., were travelling to Fort McMurray last Friday to help his retiring father pack for a move back to Ontario. It would probably have been one of their last trips north, said Hollowell.
Sennett, a 34-year-old welder, was driving his pickup truck. His daughter and an adult friend were with him.
RCMP said the truck had pulled out to pass a vehicle when it smashed head on into another pickup carrying six people.
Sennett and the friend were killed. Passing motorists managed to pull Hollowell's granddaughter from the fiery wreckage but she died in hospital.
Four people died in the other truck — a pastor, his wife, one of their two young sons and a pregnant woman.
The pastor's three-year-old son and the pregnant woman's husband survived.
Hollowell said she would like to personally thank the strangers who tried to save Faith. She also sends her sympathies to the families of the others who died.
"My minister comes to my house and we pray for everyone involved in this. It's the biggest tragedy."
She said she lived in Fort McMurray 30 years ago and was often afraid of driving the busy stretch of road, which is the main link between the oilsands capital and Edmonton.
There have been several deadly accidents on the highway. Between 2001 and 2005, more than 1,000 crashes killed 25 people and injured 257 others. The following year, after increasing public pressure, the province announced that it would twin a 240-kilometre stretch, but only 33 kilometres have been twinned so far.
The province says it will continue with the work, but it's not an easy project. The road crosses marshy terrain and several bodies of water.
Wood Buffalo RCMP say speeding is a huge problem, though they haven't linked speed to the deadly crash. Even after Friday's seven fatalities, police on the weekend handed out nearly 100 speeding tickets, including one to a man driving 184 km/h on Highway 63. The limit where he was caught was 100 km/h.
The detachment handed out 561 speeding tickets in April — nearly 20 tickets each day.
Hollowell said it's time to make the highway more safe.
"I don't understand when so many people need to travel that road — everything is brought into Fort McMurray, there's two humongous tarsands there, they're screaming for people to work there — and they make the entrance lethal."
She is one of thousands of people who have signed a handful of online petitions calling on the government to quickly finish twinning the highway. Hollowell provides a link to one of the petitions on her Facebook page, writing: "We need to dig into the budget and stop digging the graves."
Smiling photos of her son and granddaughter are also posted on Facebook. Hollowell said her granddaughter was a "shining star" who played piano and wanted to someday win "Canadian Idol." The girl lived with her mother in the Niagara region until two years ago, when she moved to Alberta to live with her father.
"My inseparable piece of pie," said Hollowell, breaking into tears. "I can't even explain how close we were."
She said funeral services for the pair will be held in both provinces.
— By Chris Purdy in Edmonton
Note to readers: This is a corrected story. A previous version had Holloway.
Also on HuffPost