From then, still fighting incredibly tough health battles, she went on to become a professional runner.
Her CV includes a long list of outstanding achievements, including fourth place in the 1,500m at the 2012 Olympic trials and, in 2014, becoming the US indoor champion in the 3,000m.
That's right: a cancer-stricken national champion runner. Grunewald crushed every stereotype of what someone with cancer could do. And then she kept on crushing them.
Despite her young age, she quickly became an inspiration to cancer patients and athletes the world over.
Over the years, she's advocated for more funding for rare cancer research as well as encouraging cancer survivors to get outside and embrace active lifestyles.
Grunewald had approximately 50 per cent of her liver removed in 2016, after a recurrence of ACC. In 2017, a scan showed small tumours on her liver. That year, she retired from professional running but still harboured the dream of competing in the 2020 Olympic trials.
It wasn't to be.
On May 4, Grunewald posted a photo of herself on Instagram asking people to send her strength as she lay in a hospital bed, fighting an infection.
The setback meant she missed her own race, the "Brave Like Gabe" 5k, organised to raise money for rare cancer research.
Even at a time of incredible physical struggle, she found the strength to use her platform to advocate. "It's not lost on me that maybe this is one of the most poignant ways to show just how critical research is," she wrote. "Cancer is nothing if not incredibly inconvenient and we need more options."
Grunewald was one of the US's most accomplished and admired middle-distance track runners. A number of her victories were cancer-stricken ones, as she struggled with the disease for 10 years, but she never let cancer slow her down.
Her charitable foundation "Brave Like Gabe" raises money towards rare cancer research and aims to empower cancer survivors to live active lives. It started when her friends tried to help ease the financial burden of Grunewald's own cancer treatments. The hashtag #bravelikegabe became so popular, the family were inundated with donations and were able to start their own charity to help others.
Since retiring from professional running, she focused her energy on her foundation and her hope for increased funding for research for cancer.
Her husband, Justin Grunewald, announced last week that his wife was being returned to an intensive care unit because of septic shock. She was then moved to comfort care.
Over the last few days, as her condition deteriorated fast, he kept her up to date with all the messages of love and support she was receiving via social media from admirers across the globe.
"Gabriele heard your messages and was so deeply moved," he wrote on Instagram. "She wants you to stay brave and keep all the hope in the world. Thanks for helping keep her brave in her time of need."
Gabriele Grunewald, forever 32, is survived by her husband, Justin; her father, Kim; her mother, Laura; her sister, Abby; and three brothers, Zack, Caleb and Ben.
Cancer may have taken her from them but her legacy will live on forever and help others, athletes or not, overcome obstacles and cross finish lines they thought impossible.
To find out more about the Brave Like Gabe Foundation, visit the website.
