Robert Jones, 43, crashed his Peugeot van into a Volkswagen Passat containing four people who were going home after a family member's birthday party on September 9 last year.
One of the rear passengers, 86-year-old Laura Roberts, was badly injured and died in hospital 11 days later.
The driver was Mrs Roberts' son Clwyd Roberts, and he was driving his family home from a party in St Martin's for his sister Alwen Jones' birthday.
Mr Roberts' partner Caroline Franks was in the front passenger seat when Robert Jones failed to navigate a bend in the road and drove onto the wrong side of the carriageway.
She suffered life-changing injuries to her ankle that affect her mobility and still require surgery.
An off-duty nurse, who was nearby, treated Jones after the crash and he began falling asleep, though she thought it was because of drink rather than injury, Shrewsbury Crown Court heard.
The court heard statements from members of Mrs Roberts' family, which described her as "the heart of the family" and described the "massive void" her loss left in their lives.
'My best friend'
Mrs Roberts had three children and 10 grand-children, and she was known affectionately as 'Doll'.
Alwen Jones' statement said that her mother lost her husband of 65 years, Will, earlier in 2018 but had started to "rebuild her life".
It said that she enjoyed shopping with her daughter, visiting a garden centre at the weekend and catching up with her children, grandchildren and great-grandchildren.
"As the only daughter we were very close and shared many secrets," she said.
"She wasn't only my mum, she was my shopping buddy and my best friend.
"Her home was always filled with laughter.
"Words will never come close to filling the massive void and emptiness that this has left in my life."
Sati Ruck, prosecuting, said that after the accident Jones was tested for alcohol and was found to have 126 milligrammes of alcohol per 100 millilitres of blood – one-and-a-half times the legal limit of 80.
Jones admitted to police that he had consumed three quarters of a bottle of wine before getting in his company van to go and see his sister.
He pleaded guilty at the first opportunity, and on Monday he was jailed for four years for causing the death of Mrs Roberts by dangerous driving.
Judge Peter Barrie imposed another two-year sentence, to run concurrently, for causing serious injuries to Miss Franks by dangerous driving.
Representing him in court, Adrian Roberts said that Jones worked in the army before becoming a roofer, and had a drinking problem.
He suffered broken ribs in the accident.
Mr Roberts said: "He feels keenly the consequences of what he does and apologises unreservedly to the family for what he has done.
"He takes full responsibility."
Jones, of Old Whittington Road in Gobowen, was also disqualified from driving for five years. To reapply after that he will have to take an extended driving test.
Judge Barrie told Jones: "You crossed onto the wrong side of the road without any explanation for why that should have happened, except for the fact that you had taken your car to drive it when you had had nearly a full bottle of wine to drink and were more than one-and-a-half times over the drink drive limit."
The judge considered Jones's drinking on the night of the accident an aggravating factor in his sentencing decision, although he was not sentenced for any drink-driving offence.
Judge Barrie also said: "It is clear that [Mrs Roberts] was a much-loved grandmother and the loss of her has been devastating for the family.
"There is no sentence that I could possibly impose which could in any way make up for the loss that the family has suffered."
Judge Barrie expressed his thanks to the family of Mrs Roberts for their assistance in the legal process.
Several members of her family, and Robert Jones's family, attended the hearing.