Gosford District Court Judge Justin Smith said Merrett, 52, had a blood alcohol level above 0.20 and was driving nearly 30km/h over the speed limit when she crashed into a car being driven by a woman with her son in the back.
After the accident, Merrett asked: "Where am I? What's happened? I need a drink, I need a drink."
She later told police the other car had come out of nowhere and she had only had a few drinks the night before after breaking up with her abusive partner and was surprised she was over the limit.
Merrett had in fact drunk a bottle of vodka the previous night.
Judge Smith said the boy's tragic death highlighted the dangers of drink driving and speeding and he had to punish Merrett to make her accountable for her actions and to try to deter others in the community from doing the same thing.
"These comments are directed at anyone who thinks it is OK to speed on our roads or to otherwise disobey the road rules," Judge Smith said on Friday.
"Have a look at this woman. Look at her victims, their families, and think about the years in prison that will result.
"None of you think this will ever be you but nor did this woman."
Merrett, of Bellingen, was jailed for five years and five months with a minimum of three years and six months after pleading guilty to aggravated dangerous driving occasioning death, causing grievous bodily harm by misconduct and possessing cannabis.
She had been sober for about a month when she relapsed after the argument with her then partner of 12 years, the court was told.
She decided to drive to the NSW Central Coast to see her mother and "started to feel darker and darker" on the trip down on January 3, 2023.
Merrett bought a bottle of vodka, booked into a motel, drank it all and blacked out.
When she woke up the next day she claimed she felt OK before getting behind the wheel.
Judge Smith said Merrett was driving at 78km/h in a 50km/h zone when she sped straight through a give way sign at an intersection in Killarney Vale about 12.45pm and crashed into a Toyota Camry.
The driver and her son had been on the way home from the shops after buying him new school shoes.
The boy had been in a booster seat in the rear left passenger side which took the brunt of the impact and was trapped in the wreckage.
The mother was treated at John Hunter Hospital for a fractured spine while the boy was placed in an induced coma after suffering a catastrophic brain injury and died three days later.
Merrett, who suffered minor injuries, tried to escape from hospital before being restrained by police.
"I just want to die, I have nothing left", she said before begging a police officer "you've got a gun, just take it out and shoot me now please".
Judge Smith said a psychological report revealed Merrett's traumatic childhood had had a lifelong impact and caused her alcohol addiction.
The report indicated Merrett had a longstanding major depressive disorder, an anxiety disorder and post traumatic stress disorder which would have been present since her early adolescence.
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