Heather Emmonds has been found guilty of murdering Tina Casey at Newcastle Crown Court today.
Emmonds claimed diminished responsibility for the attack on Miss Casey, 42, but the jury found her guilty of murder after about two hours of deliberation on Thursday.
Fifty-eight-year-old Emmonds, of Blyth Street in Seaton Delaval, will be sentenced on Friday.
Tina Casey died in her Holywell home in February 2013 after Emmonds stabbed her in the neck and abdomen.
The attack happened after a row over Emmonds’ young grandson, when Miss Casey threatened to take him to the Isle of Man.
She admitted stabbing Miss Casey, but said it came about in a moment of madness.
Miss Casey was found by police the day after she was killed, when Emmonds crashed her Vauxhall Corsa in Shiremoor and notes and the weapon were found in the car.
A statement released on behalf of Miss Casey’s family said: “We’re really going to continue to miss Tina, especially her children and the rest of the family, both now and in the future.
“No one has won in this case, both sides of the family have lost a mother, one has died and another is in jail, through tragic circumstances.
“Both sides in this case have shown great dignity and have conducted themselves impeccably throughout this trial.
“We’d like to thank the police for their support and Victim Support who have both helped the family through this very difficult time.
“We hope everyone now can start to get on with their lives and put this behind us.”
Detective Superintendent Steve Wade added: “This crime has had a devastating effect on the family of Tina Casey and I’d like to thank them for their support and courage throughout this investigation.
“This was a horrific attack which resulted in the death of a mother and has left her family bereft.
“We welcome the decision of the jury and hope that it brings some closure for the family to know Heather Emmonds will spend a substantial period behind bars. My thoughts are with them at this difficult time.”