Her parents, a husband-wife cancer research team were sceptical at first but tested out her theory in their Manchester University lab. And to their surprise, several cheap and widely-used antibiotics killed the most dangerous cancer cells.
The antibiotics fought seven of the most common cancers - including breast, prostate, lung and hard-to-treat brain tumours.
One antibiotic, doxycycline, is widely used to treat acne and is thought to be particularly promising.
It costs as little as 10-cents a day. In contrast, some of the latest cancer drugs cost hundreds of dollars a day.
Cancer charities said the research shows that the answers to some of the biggest questions are right in front of our eyes.
Professor Lisanti and his wife, Federica Sotgia, were discussing their research over dinner one evening when they decided to ask their daughter for her opinion.
The professor said: "She has heard us talk about cancer a lot and we thought it would be fun to ask her what she thought about cancer therapy.
"We asked her how she would cure cancer and she said 'Mum and Dad, I would just use an antibiotic, like when I have a sore throat.'
Rather than completely dismissing the answer, the professor did a DIY experiment, rubbing an antibiotic cream on a small growth on his face.
When the growth disappeared, he did some reading that confirmed that Camilla may have been on to something.
Unknown to Camilla, a bubbly bilingual child who wants to be a teacher, some antibiotics stop cell from making mitochondria, the tiny engine rooms that supply them with energy.
Camilla's parents showed that cancer stem cells - the deadly "mother cells" that give birth to tumours, keep them alive and ease their spread around the body - have particularly high numbers of mitochondria.
They also showed that four common antibiotics killed these stem cells in samples taken from breast, prostate, lung, ovarian, pancreatic, skin and brain cancers.
Importantly, healthy cells were not harmed.
The experiments on cells in a dish suggest that antibiotics could be used to stop cancer in its tracks and prevent it from spreading through the body - the main way it kills.
Professor Lisanti says that antibiotics could prove to be an inexpensive and safe one-size-fits-all treatment for cancer.
He now needs funding to test his theory on people, including women with breast cancer.
If they are shown to fight the disease, they could potentially also be used to prevent the cancer in those at high risk of developing it.
Several previous studies support Camilla's idea.
This includes one in which lung cancer patients lived longer after being given an antibiotic to treat an infection they had.
Some 75 per cent lived for at least a year - up from the usual 45 per cent.
In another study, tumours completely disappeared after just three weeks of taking doxycycline for an infection.
Cancer Research UK cautioned that Professor Lisanti's work was done in the lab and doesn't tell us whether antibiotics will work on people with cancer.
But Breakthrough Breast Cancer, which helped fund the research, is much more optimistic
Dr Matthew Lam, the charity's senior research officer, said: "The conclusions the researchers have drawn, while just hypotheses at this stage, are certainly interesting.
"Antibiotics are cheap and readily available and if in time the link between their use and the eradication of cancer stem cells can be proved, this work may be the first step towards a new avenue for cancer treatment.
"This is a perfect example of why it is so important to continue to invest in scientific research.
"Sometimes there are answers to some of the biggest questions right in front of us. But without ongoing commitment to the search for these answers, we'd never find them."
Camilla's parents have acknowledged her contribution to their research by naming her as an author of their study, which is published in the journal Oncotarget.
Her father said the story emphasises the importance of listening to what your children say.
Professor Lisanti said: "I thought it was very naïve to think you could cure cancer with antibiotics but at the end of the day Camilla was right.
"She usually is right about things. She always has a snappy answer that makes sense.
"I think she will become a diplomat or a lawyer, someone who has to think on their feet."
- Daily Mail
