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The 32-year-old was diagnosed with stage 4 terminal bowel cancer in December 2017 after her symptoms were not diagnosed by doctors for six years.
Tonight, Chambers and her fiance, Cameron (Cam) Mill are celebrating their engagement at the Christchurch Football Club with family and friends who have been there and supported them "all the way".
Their wedding in December is for family only.
"I feel robbed for the people I am leaving him behind, especially Cam. His love for me has never wavered," said Chambers.
On a clear and crisp morning in the last week of July, the pair went for walk to Lake Brunner where Mill's family have a holiday home.
"It was beautiful. The sky was blue and the sun shone above snow-capped mountains. Cam took me by surprise when he kneeled down and asked me to marry him. I said 'Of course'."
In her teens, Chambers developed anorexia and anxiety. At 15, she moved in with her boyfriend's family. They introduced her to cycling which she loved and it gave her a sense of purpose.
Chambers was hired by Team CMax in Italy for four seasons as a professional cyclist and triathlete. She trained up to 25 hours a week, cycling 100km at a time.
After her cycling career ended she gained degrees in business and science and a master's in nutrition.
But for five years she had nagging stomach pains "on and off." Her doctor thought she was gluten intolerant and her fatigue and anaemia were because she was an elite athlete. Cancer was never raised or detected.
"They couldn't find anything and I was made to feel like I was a drama queen and that it was all in my head.
"It's really upsetting no one picked up on cancer. Don't let anyone tell you nothing is wrong. Trust your gut instinct and get a second opinion - doctors aren't always right," she said.
After Chambers returned to New Zealand in December 2017 she had emergency surgery and 30cm of her bowel was removed. Tests in November revealed she had peritoneal disease - a rare cancer that mostly affects the elderly.
"This was a terminal prognosis with a 6 to 24-month life expectancy. I did a further two rounds of chemo to try and slow down the cancer. I have exceeded that now - I'm on month 11," she said.
Heart-breakingly, 12 days after she was discharged it was confirmed she had stage 4 cancer which had spread to her lymph nodes and lungs. It was incurable.
Chambers, 32, stopped chemotherapy treatment in June. She is now having palliative care.
The doctor who failed to original diagnose her cancer phoned Chambers to apologise for the error made.
"My doctor rang me a lot but I stopped answering the phone after a while. I was left feeling I needed to reassure her and make her feel better. She said she has learned from what happened and is more aware but unfortunately she didn't do it in time for me. I was the one who lost out."
A scan this week has showed the cancer has progressed slightly and she is being referred for a bone scan. Chambers has lost more weight and can only stomach oats and plain toast. She is taking Oxycodone which makes her "feel like a zombie on another planet".
Mill, a drain layer who works for an excavation company met Chambers in an Auckland café not long after she was diagnosed with cancer.
"Britt is really loving, outgoing and courageous," he said.
"She's not a girly-girl who likes to sit around. She is very adventurous and that's what I was looking for. She rides her bike whenever she can and constantly pushes herself. Even though she is unwell she does more than a healthy person, which is so amazing."
"Britt doesn't look sick. Physically her body on the outside is perfect. You wouldn't think she has a terminal illness. It's only at home when you see she's not well and her insides are being eaten away. It is heartbreaking. But to me, she is beautiful in every way".
Chambers has ticked off most of her bucket list which was to go to the Islands and get married. Her "last wish" - to do an ironman - is "on hold."
She never thought she would grow old or have children until she met Cameron's parents, John and Josie.
"I love them. They treat me like their own daughter and have taught me what family means. My whole life I never pictured myself growing old. I had mental health issues and attempted suicide twice. I wasn't super maternal but meeting Cam and his family has changed that. Having kids of our own was something Cam and I definitely wanted."
Mill also feels robbed he won't be a father or grow old with his fiancé. The couple now "live for the moment".
"It's hard to think about missed opportunities. I am 33 but how long is it going to take for me to get over Britt when she does go. I will never stop loving her. She got robbed by the devil cancer, but I feel lucky to have had the time with her which I will always cherish."
Chambers wants her ashes to be sprinkled at Lake Brunner, her "special place", where she feels at peace.
"I want to be remembered as someone who has inspired and motivated people in some way to do things they thought they couldn't. Go live your life and don't worry about what other people think."