Now the 22-year-old is an Olympic gold medallist at her debut Games, ending the reign of her childhood idol and two-time champion Mariana Pajon of Colombia.
Shriever returned to British Cycling in 2019 after UK Sport shook up its approach to funding and was able to invest in the rider.
"Honestly, I'm in shock,” Shriever told BBC Sport afterwards. “To even be here is an achievement in itself.
"To make a final is another achievement in itself. To win a medal, let alone a gold medal… I'm over the moon.
"Winning a medal wasn't my goal; results are out of our control. I just managed to hold and earn the win. It is crazy."
Moments before her historic medal win, Shriever had watched compatriot Kye Whyte win Britain’s first-ever BMX medal by finishing second in the men’s final.
The pair celebrated wildly after Shriever’s race, with the 22-year-old later revealing she had nearly been in tears when he won silver.
"I was watching him as I was going up. I was almost crying because he got a silver. I had to keep my cool and reset and just dig in. I gave it everything," Shriever added.
Whyte has his own inspirational journey to Tokyo, battling back from serious injury that ruled him out of the 2019 Olympics test event.
Affectionately known as the Prince of Peckham Whyte, 21, is the second member of his family to compete in the sport, with brother Tre winning bronze at the World Championships in 2014 before retiring last year.
"The medal means everything to me," he told the BBC. “It’s a once-in-a-lifetime opportunity. It’s hard to get to the Olympics in the first place.
"To do well and get a medal is special."
Whyte paid tribute to his family and members at the Peckham BMX club who had stayed up late to watch his final.
"I reckon Tre might cry. My dad definitely did cry and my mum cried too. When I get back it will be crazy," Whyte added.