Mary McConnell, 83, died following the blaze in the East End of Glasgow on Wednesday night.
One neighbour said two passers-by broke down the door to the pensioner’s house in Hermiston Road, but were unable to get in through the smoke.
Firefighters wearing breathing apparatus rescued her from the house, but paramedics pronounced her dead at the scene.
A neighbour, who witnessed the blaze but asked not to be named, said two men tried to get into the semi-detached property after seeing thick smoke billowing from an extension.
“There was a lot of smoke coming from a window in the house extension,” he said.
“Two fellows who were passing by kicked in the door and a big cloud of smoke came out. They tried to get in, but there was just too much smoke.
“One of them shouted ‘Is there anybody in there?’ But you couldn’t see a thing. It was thick, black smoke and it blocked the whole road.
“When the smoke came across the street, I couldn’t breathe, so what chance did that old lady have?
“I think Mary stayed there by herself but she always seemed to have a lot of visitors.
“She was a nice person and something like this is tragic at any time, but it just makes it worse when it’s Christmas.”“
Incident Commander Martin Miller said that three fire appliances had attended the blaze and six firefighters had fought it using high pressure hoses.
“We got the fire under control quickly and simultaneously rescued an elderly female from the property,” he said.
Cmdr Miller said that although the blaze was under control soon after firefighters arrived, it was hard to extinguish completely and crews had remained there through the night and throughout yesterday.
There was no damage to the adjacent property and nobody else was injured in the fire.
Police Scotland and Scottish Fire and Rescue have launched a joint investigation into the cause of the blaze, although it is not thought to be suspicious.
In a separate incident on Christmas Day, three children, including a baby, were taken to hospital as a precaution after a house fire.
The blaze broke out in an upstairs room of a two-storey property in Auchengreoch Avenue in Johnstone, Renfrewshire, at about 8.10pm.
Firefighters wearing breathing apparatus entered the building and put out the flames.
A spokeswoman for the Scottish Fire and Rescue Service (SFRS) said: “As a precaution, three children, the youngest being 10 months, were taken to hospital and three adults were checked at the scene.”
The children were taken to Paisley’s Royal Alexandra Hospital for a check-up.
Last night, am SFRS spokesman called on people to be vigilant and careful during the festive period.
“There are more house fires in December and January than at any other time of year and SFRS is eager for the public to take action to protect themselves and those around them from fire within the home.
“Anyone who keeps an eye on a vulnerable relative, friend or neighbour can make a real difference – potentially saving their life – by putting them in touch with SFRS.
“Public awareness of fire risks has undoubtedly increased and more properties than ever are now, but SFRS knows fire is a constant threat the public need to help prevent.”