After Mrs Peeters, 37, was diagnosed with breast cancer in October last year and began treatment, her energy levels dropped to extreme lows.
The chemotherapy, radiation and other drugs left her feeling lethargic and she spent many days unable to get out of bed.
But after being introduced to Pink Pilates, a pilates group for women with cancer, Mrs Peeters rekindled her spirit and became empowered to regain her fitness.
"I've had quite a way to go to get my fitness up from zero to be able to run 5.5km."
"But I've run the [course] so I know I can do it."
Yesterday she went for a run with her son William, now 11 months old.
The Tinman Triathlon is her first triathlon event and she's doing the running leg as part of a team with two of her friends. Her husband Richard, her sister and her sister's husband are also competing in a separate team.
"While I went through it physically, all these people around me went through it emotionally... so this is a nice way we can all do something together after a terrible year."
"I didn't realise how sick I was until I've come out the other side and now I'm feeling great."
Mrs Peeters and others have raised more than $2000 for the Pink Pilates trust, which helps fund Pink Pilates programmes for women recovering from cancer. They hope to raise $2500 by Sunday.
"It's been hard work but exciting getting to where I'm at.
"One of my friends has even said we should do it again next year and compete on our own, who knows, but this has been really good for us."