Melanie Koch is quick to dismiss any suggestion her sister struggled or battled her way through a stubborn form of cancer.
In fact, her sister Sophie Smith's stoic attitude to being diagnosed with Hodgkin's lymphoma gave Mrs Koch hope that her biggest supporter may be fit enough to greet her at the finish line of the HBF Run for a Reason at Gloucester Park tomorrow.
But a devastating development in Ms Smith's condition means her family are now pacing the 12km circuit in memory of the 27-year-old who died from pneumonia five weeks ago.
Mrs Koch will wear the number one bib as the biggest fundraiser in the event after more than $40,000 was donated to the Australian Cancer Research Foundation in honour of Ms Smith.
A personal trainer, Mrs Koch had set out to promote fitness and raise money towards researching a cure for rare cancers.
About six months ago, the family received their biggest indication Ms Smith may be able to overcome her illness when she was declared disease free and attended her sister's wedding.
"Things were looking good and she looked amazing and you would never know she had any type of cancer," Mrs Koch said.
"She had lost her hair so she wore a headscarf but other than that she looked radiant and happy and just like a normal person."
Weeks later, after noticing a pain in her side, Ms Smith received the heartbreaking news the cancer had returned and there were no other treatments available for her.
Ms Smith moved from her home in Sydney to live with her distraught Perth-based family. Mrs Koch said her sister's resilient attitude in her final months kept the family in high spirits despite the uncertain outlook for Ms Smith.
"She never complained about anything and all her friends thought that was really inspirational," she said. "I'm extremely proud of her."
Mrs Koch will be joined by her parents Elizabeth and Keith Smith and close family in honouring Ms Smith as they cross the finish line "for Sophie" tomorrow. "We're all so grateful for the donations we've received," she said.
"It will be an emotional day, the whole time my sister had lymphoma we were all so supportive and everyone was around us which is the same as now.
"She wasn't a very spiritual person but she knows I was going to do the event. She'll know and she'll be around."
More than 30,000 people are expected to enter the event.
Registrations will be held at Perth Arena today until 4pm.
The Bureau of Meteorology has forecast showers and temperatures up to 20C the run.