If the 18-year-old's brittle bones were to break as she jumped up to attend to five-month-old Casey-Lee in her cot, the aggressive form of cancer would quickly spread.

Emma relies on the support of her mum and dad, Janine and Graham, who have stepped in to care for both her and her daughter after her shock diagnosis.

The pain in her right hip had started just before the birth of Casey-Lee but it was initially put down to labour pains - however the pain persisted after she gave birth.

"Two weeks before Casey was born I started getting pain and struggled to walk, but I was so close to labour that I thought it was related to that and the doctors agreed," Emma said.

"After I had Casey the pain only got worse and it was then diagnosed as sciatica, and after that as a twisted pelvis.

"I underwent physiotherapy and was then treated by a chiropractor who sent me back to my GP for more tests."

Eventually on May 1, after seeing a number of specialists and undergoing an array of testing, Emma was diagnosed with osteosarcoma, a rare and aggressive form of bone cancer.

For the next eight months, or more, she will undergo intensive treatment at the Chris O'Brien Lifehouse centre as she fights for her life - and her daughter's future.

"Everything I do, I do for Casey," Emma said. "I had to choose whether to get my eggs harvested, which would have delayed my treatment by a month.

"I already had Casey so I chose to get my treatment started as soon as possible, to give me the best chance to beat this and be there for my daughter. When I'm undergoing chemo all I do is think of her and I can't wait to get home to see her little face."

Mrs Drummond, who has recently battled breast cancer, cares for Casey-Lee while Emma is in treatment while Mr Drummond stays by her side at the Sydney cancer centre.

"The chemotherapy drugs are toxic so Emma can't provide full-time care for Casey during treatment," Mrs Drummond said.

"But Casey's face lights up when her mum comes home and Emma is trying to do as much as she can between treatments.

"If she can feed her her bottle she does, if she's too weak she will watch as I feed her. I'm trying to make sure that Emma is able to be there for all her 'firsts' - her first try of solids and so on - I don't want her to miss out on too much."

After three months of intensive chemotherapy Emma will undergo radical surgery which will see the diseased bone in her hip replaced. Further chemo will hopefully ensure the cancer does not return.

Emma's two older siblings have set up an online fundraising page to help their parents and sister out with medical and living expenses.

Mrs Drummond has had to give up her casual work as a teacher's aid, and Mr Drummond has to take leave without pay to take her to treatment.