It was a tragic double-blow that would test the Hopkins' family resolve to the limit.
While young Arna still lives with daily pain, treatments for her healing skin grafts and more surgeries next year, the Hopkins family are making progress.
"Within herself, she's a lot better. She's starting to get her spirit back, which is really nice," family spokesman Kane Hopkins, Arna's uncle, said this week.
Arna is being helped along the road to recovery with loving fun from her brother Seb, 5, and 6-year-old sister Claudia.
They're able to "do some more normal stuff", playing together on the family farm near Martinborough and are even enjoying a family holiday away this festive season.
But it's been hard work, and the Hopkins family know there's still long way to go.
Arna's parents - mum Penny is a teacher, and Regan a farmer - massage the scar tissue daily, which is painful for the battling toddler.
She has also suffered infections, which Kane Hopkins says was expected, and is confronting the publicness of her burns to her body and face. "Dealing with stares from other kids and things like that are tough," Kane Hopkins said.
Where her joints are burned, the scarring is "very painful," he added.
Her father Regan knows something of her suffering, as he badly burnt his fingers and hands trying to save her when her clothes caught alight.
"I was talking to my brother about his injuries on his fingers and hands, and he said the nerve damage, which you don't see, is where a lot of the pain is for them," he said.
"From early next year she'll be looking at further surgeries, and that will continue for the next couple of years at least."
The wider Hopkins family has been amazed at the resilience of Penny and Regan.
They're enjoying a break away, which Mr Hopkins said was crucial for them.
"They've been hit by a series of things, Mila ... and then Arna, and a few other things that have happened.
"The fact they're in good spirits and are as positive as they are now is just a credit to them. It's quite incredible."
"They're with family and friends over Christmas and New Year. For them, it's a pretty important time, to reconnect with others, after being quite insular this year."
A Support for Arna Fund was set up to help the family with travel and accommodation costs after the accident.
Kane Hopkins said the generosity of the local community, including from people the family did not even know, was "quite overwhelming".
It's helped them survive a year from hell, he said.
"They've been completely and utterly humbled by it." APNZ
