When placed on a normal diet in April 2018 and given extra support, she quickly began to grow and her teeth emerged.
Speaking out about the horrific case of child neglect, the My Kitchen Rules host said it was wrong to forbid a child to eat meat.
"This is so, so sad," the paleo chef lamented in a Facebook post, linking to news.com.au's article.
"I will repeat it again and again. Humans are omnivores and we are designed to eat meat in our diet. Children should not be on a vegan plant-only diet."
The 46-year-old TV personality and cookbook author urged people to "please use common sense", especially when it came to their kids' diets.
"If you choose to eat a plant-based diet as an adult then that is your choice and go for it … but please, please be wise with choices of what you feed your children."
But some commenters argued the case had nothing to do with veganism, which forbids all meat and animal products, including eggs and dairy, and was merely a case of neglect.
"The fact the diet was 'vegan' really has nothing to do with it. It was simply inadequate," one Facebook user said.
"There are vegan diets of crap pizza, pasta, chips … and vegan diets of wholesome organic vegetables and produce. There is a HUGE difference," another said.
Doctor's warning for parents
Research by Cardiff University in Wales last year concluded "relying on only plant-based foods to provide all a baby's needs is not out of the question, but is less than ideal"
"Even a varied vegan diet has the potential to cause a range of problems for babies' growth and development," the study found.
In May this year, the Royal Academy of Medicine in Belgium issued an opinion that veganism for children is "unethical" because it is extremely difficult to feed a child a balanced vegan diet.
The official opinion will make it possible to punish parents who force their kids to follow a vegan diet with fines and even jail time, under the crime of "non-assistance to a person in danger".
"We must explain to the parents before compelling them," said Professor Georges Casimir, who led the commission that wrote the report, "but we can no longer tolerate this endangerment.
"When we are children, the body manufactures brain cells. This implies higher requirements for protein and essential fatty acids. The body does not produce them, it must be brought in via animal proteins.
"We are talking here about stunted growth and psychomotor delays, undernutrition, significant anaemia. Some developments must be done at a specific time in life and if they are not done, it is irreversible.
"It is not medically recommended and even forbidden to subject a child, especially during periods of rapid growth, to a potentially destabilising diet, requiring frequent supplementation and control."
In 2015, an Italian court ordered a mother to cook meat for her son after the boy's father complained she was harming him by restricting his meat intake. Also in Italy, a couple lost custody of their 14-month-old after doctors believed a vegan diet had led to the baby lacking fundamental nutrients, worsening his unrelated congenital heart condition.
However, there are mixed opinions about the appropriateness of a vegan diet for children.
The American Academy of Paediatrics states: "Although there have been case reports of children failing to thrive or developing cobalamin (vitamin B12) deficiency on vegan diets, these are rare exceptions.
"Multiple experts have concluded independently that vegan diets can be followed safely by infants and children without compromise of nutrition or growth and with some notable health benefits."
PETA (People for the Ethical Treatment of Animals) executive vice-president Tracy Reiman told news.com.au that a "proper" vegan diet was healthier than one packed with junk food.
"Depriving children of essential nutrients is what's abusive, and that can happen on a diet of carcinogenic processed meats, but it cannot occur on a proper vegan diet, which is rich in leafy green vegetables, beans, legumes, grains, seeds, fruits, and nuts — ie, chock-full of vitamins, minerals, and calcium," Ms Reiman said.
"A proper vegan diet," she added, "is strongly endorsed by the US Academy of Nutrition and Dietetics because it sets a child on the path to a healthy old age, rather than to the intensive care unit with heart disease, diabetes, cancer, a stroke, or high blood pressure."
The Dietitians Association of Australia warns against a vegan diet for children in the first years of life, instead recommending children in this age group eat dairy products and eggs.
For older children, the DAA says, a carefully planned vegan diet can be sustainable with vitamin B12 and D supplements, but a doctor and accredited dietitian should be consulted.
Child was "floppy"
Court documents showed the malnourished Sydney toddler's mother told doctors her daughter would generally have one cup of oats with rice milk and half a banana in the morning, and a piece of toast with jam or peanut butter for lunch.
For dinner, she said her daughter would be offered tofu, rice or potatoes. But she said the girl was a "fussy eater" so she might just have oats again.
This diet resulted in severe deficiencies in nutrients across the board for the infant, including a lack of calcium, phosphate, vitamin B12, vitamin A, iron and zinc.
Her levels of vitamin D, which can cause bone disease if found to be too low, were "undetectable".
Rickets is a preventable bone disease that affects babies and young children and causes soft and weakened bones. Children are typically diagnosed with rickets due to a lack of vitamin D, calcium or phosphorus.
The girl's condition was only brought to the attention of doctors in March last year, when doctors attended to the infant after she suffered a seizure.
She was just over a year old, but weighed only 4.9kg, which is barely double of what she weighed when she was a newborn.
One doctor described her as "floppy" and said the tiny one-and-a-half-year-old didn't crawl or talk during the month in care, according to court documents.
In an investigation into the girl's medical history, doctors found an absence of immunisations, no follow-up check-ups after she was born and no birth certificate or Medicare number.
The toddler's two older brothers, aged six and four, are also in government care and were also on vegan diets.
