Mr Justice Peter Fraser said Jennifer Johnson’s lies struck at the heart of the administration of justice.
He said Johnson remained silent for decades despite knowing she had lied to protect a murderer.
“Your dishonest support of Bishop lasted a number of years,” he said. “You did not finally tell the truth until 2019.
“The effect of your dishonesty lasted for three decades.
“Having seen you give evidence over three days, it is difficult to believe anything you say.
“You are an accomplished liar.
“You wanted Bishop home with you, not in prison.”
Johnson, 55, refused to leave her cell or appear by video, the court heard.
She would have stood in the same dock where her lies helped to acquit Bishop in 1987, leaving him free to attack a third little girl.
Johnson lied about vital evidence linking him to the murders of nine-year-old friends Nicola Fellows and Karen Hadaway – claiming a blue sweatshirt linked to the scene did not belong to Bishop.
Bishop walked out of court and, three years later, attacked a seven-year-old girl and was jailed for life.
New DNA techniques proved the blue sweatshirt was his and he was jailed again at a double jeopardy retrial in 2019 following a change in the law.
Johnson, who had three children with Bishop, continued to back him until detectives from Sussex Police said they wanted to speak to her about perjury.
She tried to argue she was compelled to lie for Bishop despite him being jailed for life.
Following a four week trial, Johnson was convicted of perverting the course of justice and perjury on Wednesday.
At the sentencing today, she refused to leave her cell or appear by video link.
The families of Karen and Nicola criticised Johnson for failing to come forward to admit her lies.
She took the cowards way out, cousin Lorna Heffron said.
After Johnson failed to appear in court to hear her fate, Chris Henley QC for the defence asked the judge not to hold it against her.
The dock at Lewes Crown Court number one remained empty as Mr Justice Peter Fraser said Johnson had lied and lied again.
“Both offences strike at the heart of the administration of justice,” he said.
“The effect of your evidence at the trial was that Bishop was acquitted of these two murders.
“There was another dreadful consequence of your actions. He was free to attack again and he did.”
Johnson’s lack of truth was remarkable, the judge said.
Bishop refused to leave his cell after giving evidence at his Old Bailey retrial.
He was not in court when he was given life with a minimum 36 years for the horrific murders at Wild Park in 1986 which became known as the Babes in the Wood.
A four week trial at the same court where Bishop was tried twice heard Johnson was at the heart of the plan to pervert the course of justice before the 1987 trial.
She changed her story in the witness box at the same court where she was sentenced 35 year later.
Representatives of the Hadaway and Fellows families, spread out at 2m distances, sobbed as the victim impact statement was read by Karen’s mum Michelle.
In the final line of her emotional statement, Michelle asked the empty dock: “What you must now ask yourself is, was it worth it?”
The only member of Johnson’s family in court to hear the sentence was the fourth child she had with her late husband who she married after Bishop was jailed.
She sat in the upstairs public gallery and wept quietly throughout the hearing.
Speaking after the sentencing, Michelle Hadaway said: “I don’t know if any sentence would be good enough.
“She has to sit behind bars the next six years.
“At the end of the day, she has to sit there and think, Was it worth it?
“I wasn’t really surprised she didn’t come to court.
“He [Bishop] didn’t come to court to hear his sentence.
“We have had to suffer and have had to go on suffering, knowing the evidence of the sweatshirt was very, very important.
“She had ample chances to come forward years ago.
“It’s all about choices.
“Of course she had the chance to do what was right.
“You swear to tell the truth and that is exactly what you should do.
“Do we ever get closure?
“To Jennifer Johnson I say, was it worth what she put her children through?
“Only after he was convicted, she chose to say she told lies all those years ago.
“It’s heart breaking, but we have to live with it every day.
“Has she ever inside her heart any sympathy for what we have gone through? No, she has not.
“To me, it’s like it was only yesterday. It never goes away.”