Tragic Danielle Saunders, 29, was discovered by emergency services at her home.
Her tree was still up and there were several presents and toys for her three children scattered underneath.
A coroner heard Danielle, of Saltash, Cornwall, dropped a lit cigarette onto the toys and cardboard on the floor which accidentally set a fatal fire that consumed her lounge.
An inquest held in Truro, Cornwall, on Tuesday heard how Danielle had been out drinking in Saltash town centre with friends the previous evening.
DC Heather Gibbs told the inquest police were alerted on December 30 by a friend who was concerned that Danielle had been inactive on Facebook for longer than usual.
When the friend arrived at the property, located near the bottom of the Tamar Bridge, she could see a blackened door inside and hear an alarm sounding.
Police were called and officers discovered that the front door was locked, although they were able to gain access through the back door.
"They could smell smoke, they went inside and they found Danielle behind the sofa," DC Gibbs said.
"The police asked for fire and medical responders who arrived, and Danielle's life was pronounced extinct by a paramedic at 2pm on the 30th.
"The room was very blackened. There had obviously been a lot of soot or smoke in the room.
"The seat of the fire started just in front of the Christmas tree where there were some boxes and toys and bits and pieces.
"It would have been a slow-burning, smouldering type fire rather than flames, caused by some material such as a cigarette.
"She had a blanket with her, sort of a fleece, so it looked like possibly she had perhaps woken up and realised that the room was full of smoke and had probably got down on the ground, which is what TV adverts tell you to do, done the right thing to get out and then perhaps become disorientated."
Danielle had three children, none of whom were inside the property at the time of the incident.
A pathologist, Dr Russell Delaney, concluded that Danielle died as a result of fire fume inhalation.
Her judgement may have been affected by medication and the consumption of alcohol the previous night, Dr Delaney said, although the position of her body did not suggest she was incapacitated.
Following an investigation, Saltash fire station manager Mark Goldsmith confirmed that the most likely cause of the fire was careless disposal of smoking materials.
Mr Goldsmith concluded that when Danielle returned home after her night out, she must have lit a cigarette while sitting on the sofa close to the Christmas tree.
"Whilst smoking the cigarette Danielle fell asleep and dropped the cigarette onto the toys and the cardboard and materials on the floor between the sofa and Christmas tree," Mr Goldsmith said.
"After a period of time these materials ignited causing a fire. As the doors were closed the fire produced thick black smoke which Danielle breathed in when Danielle woke and became aware of the fire and smoke.
"She was probably disorientated and trying to escape from the lounge. Due to the smoke she breathed in she was unable to escape and was located behind the sofa."
In a short conclusion, assistant coroner for Cornwall Barrie van den Berg said: "A fire started which led to a fatal inhalation of fumes from the fire."
Addressing the family, he added: "Can I express my deepest sympathies, because there's nothing as bad as losing a child, no matter how old they are? It's heartbreaking."