The family of a woman who died after a 12-year-old allegedly lit a fire at the foot of her bed say they're still grieving.

The woman died in hospital in 2020 after suffering burns to 70 per cent of her body and lacerations after she climbed out the window of her burning bedroom.

"We are still grieving and feeling the loss of her presence every day," the woman's son told Open Justice as the teen accused of her murder appeared in court today.

"She has left a massive hole in our lives that may never be filled but we thank all those who have helped us through this devastating time.

"We place our trust in the NZ police and the courts to enact justice for Mum."

The now 14-year-old pleaded not guilty in the Palmerston North District Court this morning and is due to stand trial for murder in March.

The boy's name and that of the victim are both suppressed.

The boy is alleged to have taken a petrol canister from the woman's garden shed on the evening of December 2020.

Just before midnight he allegedly poured the petrol at the foot of her bed while she was sleeping. Police allege he then ignited it with a piece of burning paper before leaving the room and closing the door behind him.

The summary of facts alleges the boy then ran to a friend's house where he told the family there that there was a fire at the address.

Meanwhile, the woman awoke to find her bedroom engulfed in flames.

Police allege she stepped through the flames, smashed her bedroom window and managed to climb out.

She was found on her front lawn with significant burns and cuts.

The woman was then taken to Palmerston North hospital with burns to more than 70 per cent of her body as well as fire-inhalation injuries.

However, she died the next morning due to her injuries.

- Jeremy Wilkinson, Open Justice