But choosing Mila's was not.
"Usually on the back of my Christmas cards, I put a family photo."
"I don't have a particularly good updated family photo of me, Clarke and Neve.
"So this year, courtesy of Mila, who is 12, we're going to be using [her portrait] on the back of all of our Christmas cards.
"Thank you Mila for my updated family portrait."
Mila said she was delighted the Prime Minister had singled out her portrait.
"It's cool. It's pretty special."
It was quite a surprise, she said.
"They didn't send me an email, so I didn't really know I had been selected.
"Dad was scrolling through his Instagram and watched [Ardern's announcement] to see who won it, not thinking that we had gotten it.
"We watched it and then Mum and Dad screamed and Mum started crying."
It is not the first time Mila's art has been recognised.
She was shortlisted for J.K. Rowling's Ickabog illustration competition earlier this year, in which tens of thousands of young artists around the world entered artworks to illustrate Rowling's fairy tale The Ickabog.
Mila is the daughter of award-winning Dunedin artist Simon Richardson, and no doubt she is a chip off his block.
But when asked where she thought she got her talent for art from, she simply answered, "Myself".
"Not my dad. He does different art."
Ardern said the Christmas card entries would be exhibited at Parliament over the next few weeks.
