"She had dropped a tonne of weight and she looked brilliant," she said.
"It shows that it doesn't matter if you are healthy or if you are unhealthy, cancer can be a ticking time bomb."
Like other Kiwis hit by cancer, the suddenness of Awhitu's death was particularly devastating.
During their short friendship, Dunn had already come to rely on Awhitu's positivity to help her motivate those in her fitness class.
Describing herself as a hard taskmaster who "didn't really do excuses" from her clients, Dunn said she learned a softer approach after watching Awhitu.
"She taught me that sometimes there is more than meets the eye and to give people the time to explain themselves," she said.
"I learned how I can lead better."
But just as Awhitu was coming into her own, she was diagnosed with terminal stomach cancer and given one year to live.
As chemotherapy weakened her immune system, she was also ordered to stay out of the gym to avoid health complications.
"One thing we specialise in is helping people through tough times, but we couldn't help her because she wasn't there," Dunn said.
The Smash Fit women instead found other ways to help.
They started bringing food each week for Awhitu's family and when Christmas came they bought presents for her youngest children.
By January, a ray of light emerged as Awhitu texted Dunn to say she was responding well to chemotherapy and was hoping to travel to America to see her son's new baby.
This became her "driving force to keep living", Dunn said.
Dunn offered to do a fundraiser at the Papakura gym to help Awhitu make the trip.
But before it could be organised, Awhitu became ill with headaches and it was found the cancer had spread to her brain. She died on February 20.
At Smash Fit that night, Awhitu's "devastated" classmates held a fitness class in her honour.
"It was the most passionate class I've ever been a part of. There was something special about that class," Dunn said.
Awhitu left behind Charlie and five children, aged between 6 and 26, so Dunn and her team are planning a new fundraiser.
Sixty of Awhitu's former gymates are now set to climb on gym bikes on June 16 and pedal continuously for 24 hours in teams.
All money raised through Awhitu's givealittle page will go to her family.
Dunn hopes it shows Awhitu's family how much she meant to her friends at the classes.