Rita Wharton died when her car was hit after Anita Corless tried to overtake traffic near Welshpool, Powys.
Corless, 58, originally from Milford Haven in Pembrokeshire, admitted causing death by dangerous driving.
She was given a 16-month prison sentence at Mold Crown Court.
The driving instructor said she had no memory of the fatal manoeuvre on the A483 road between Welshpool and Pool Quay, last March.
The court heard on Tuesday how she was in a line of traffic on a straight stretch of road when she pulled out but there was insufficient room and she caused the crash.
Mrs Wharton's Ford Ka, the second in line, was struck by two vehicles.
A widow, said to be the lynchpin of the family, Mrs Wharton was declared dead at the scene.
"You quite inexplicably drove your vehicle into the face of on-coming traffic in an overtaking manoeuvre that was obviously dangerous," said Judge Niclas Parry.
"On-coming vehicles should have been visible to a careful driver.
"You are by profession a driving instructor, employed by Lancashire County Council to run speed awareness courses."
Speed awareness courses are offered by councils and police forces across Britain to avoid penalties for minor speeding offences.
Corless, who was living in Bentham in North Yorkshire at the time of the incident, was herself seriously injured in the crash.
The judge told her it was a thoroughly-avoidable fatality which "must be marked by a custodial sentence".
In addition to the 16-month jail sentence, Corless was banned from driving for two-years and eight-months, and must take an extended driving test before being allowed back on the roads.
The court was told that, despite her age, Mrs Wharton still worked as the head housekeeper at a pub in Powys, and lived her life like a woman in her 50s.
In family impact statements, victim she was described by her daughter Diane Dunderdale as "my best friend and my rock".
A driving instructor heading to teach a speed awareness class has been jailed for causing a five-car smash that killed an 83-year-old woman.