Her vehicle was travelling along State Highway 8 from Fairlie towards Tekapo and appeared to have lost control, left the road and hit a tree, police said.
Two passengers in the vehicle were taken to Timaru Hospital with moderate injuries. No other vehicles were involved.
Speed, the vehicle's poor condition and bad weather were believed to be contributing factors, police said. Ms Margaret was not believed to have been wearing a seatbelt.
A second fatal crash on Canterbury roads occurred about 3.15am today when an 80-year-old male pedestrian from Ashburton was struck by a vehicle on the Hinds-Rangitata Highway, approximately five kilometres south of Hinds. He died as a result his injuries.
Early police enquiries suggested he may have been driving south before parking his vehicle and continuing south on foot.
The driver of the vehicle which hit the man stopped, and had been spoken to by police.
The dead man's name would not be released until a formal identification process had been completed and next of kin had been notified, police said.
Timaru police were appealing for anyone who was travelling on the Hinds-Rangitata Highway near the Hinds township at that time, or who may have seen the man walking on or near the road to contact them on (03) 687 9808.
They were also appealing for sightings of a white Nissan Pulsar found parked within a few kilometres of the scene.
Another motorist died following a four-vehicle crash in the west Auckland township of Kumeu around 7pm last night.
Several others were seriously injured in the crash, police said. Three people were taken to hospital, one in a critical condition.
The serious crash unit was investigating.
Meanwhile, an elderly man died today after crashing his car into a tree while driving in heavy rain near Pukekohe yesterday.
The 74-year-old was left in a critical condition after smashing into a tree at the intersection of Tuakau and Buckland Roads, about midday.
The Counties Manukau police serious crash unit was investigating the incident and were seeking more information on the vehicle leading up to the time it crashed.
Anyone who saw the man's black Isuzu Bighorn, registration WE2879, before midday yesterday was asked to contact Constable Amy Weston on 09 261 1302, or to leave information anonymously through Crimestoppers on 0800 555 111.
