Daniel Smith, 31, from St Issey, was found guilty of causing death by dangerous driving at Truro Crown Court.
Sabrina Bellman, 28, from Hampshire, died on Boxing Day 2015 after the car she was in collided head-on with Smith's car at Washaway, Cornwall.
Her husband, mother-in-law and two-year-old daughter were injured.
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The court heard Smith was doing at least 57mph on a road with a 50mph speed limit, and was on the wrong side of the road.
Mrs Bellman was in a car being driven by her mother-in-law.
They were on their way back to a holiday lodge near St Tudy, having watched a pantomime in Exeter, when the crash happened.
Sentencing, Judge Robert Linford said: "It was not safe for you to travel at that speed.
"The death of Sabrina Bellman was caused by one thing; you driving too fast."
Smith had previously admitted causing death by careless driving.
He was also found guilty of causing serious injury by dangerous driving, and sentenced to 18 months for each offence, to run concurrently.
Speaking outside court, Mrs Bellman's husband, Dominic, said: "Sabrina was the most beautiful, kind, loving person I've ever met.
"I'm now going back home to my four-year-old daughter to try and put our lives back together, the lives that Daniel Smith tore apart.
"I hope this verdict sends a message to the public to not drive dangerously."
During the trial, Smith, a divorced father-of-two who works as a youth worker, said what happened would "stay with him forever".
"I wish it was me that died in the crash and not her. I am so terribly sorry for what happened," he said.
A driver who caused the death of a young mother after a Christmas pantomime has been jailed for four years.