Emergency services were called to the scene at Main Road, where the A78 Largs to Seamill road was closed to traffic.
The woman's 60-year-old husband and the lorry driver, 54, were rescued and taken to hospital with minor injuries.
The building is split into five homes and the couple had been watching television in their bottom-floor flat.
One other man who was in the building at the time was evacuated unhurt.
Another resident Callum Calvey had been out at work when the lorry struck the building at about 13:45.
"My bathroom has been wiped out," said the 21-year-old tree surgeon, who lives directly upstairs from the the couple.
"There are five flats and none of the other residents are about, but I believe the couple's dog got out as well."
Photographer Arlene Foster, who works for Anna Conway Photography, was quickly at the scene from her local shop.
"The lorry is literally in someone's front room," she told BBC Scotland.
"The lorry seems to have been going towards Ardrossan but hit the building on the opposite side of the road.
"Fortunately, it was quite quiet at the time - school kids could have been affected as well if it happened later."
Police are urging drivers to stay away from the area, with southbound traffic being diverted at Largs onto the A760 at Hayley Brae and northbound traffic being diverted at the Hunterston Roundabout.
The local community had been pressing for a widening of the main road to Hunterston power station and Clyde Port.
Steve Graham, chairman of Fairlie Community Council, said: "This was an accident waiting to happen.
"There have been a number of near misses, but nothing on this scale. It is a very narrow road with premises adjacent to the road.
"We in the community council have been complaining about the weight of traffic coming through the A78, which it's not built for. It would not meet current standards for a trunk road."
A Strathclyde Police spokesman added: "The ground floor of the building has been seriously damaged and has been deemed structurally unsound."
A 55-year-old woman has died after a couple became trapped under rubble when a coal lorry ploughed into a house in Fairlie, Ayrshire.