A mother-of-six who slashed her sister-in-law in the face with a Stanley blade in a busy shopping centre has been sentenced to four years in prison, with the final two years suspended.

Mary Maughan (39) from Palmerstown Woods in Clondalkin pleaded guilty at Dublin Circuit Criminal Court to assault causing harm on November 29, 2011 at the Mill Shopping Centre in Clondalkin, Co Dublin.

The court heard that a “red mist” descended over Maughan when she saw her “nemesis” sister-in-law.

Garda Kamil Pawel Linder said that Teresa Maughan had been shopping in Dunnes Stores when she saw Mary Maughan approaching.

Mary Maughan shouted “RIP” and “you’re dead, whore” while taking something from her sleeve.

Teresa Maughan pushed her trolley at Mary Maughan and ran away but was dragged back by the hood of her coat.

She said she felt a scrape on her face and then a warm sensation of blood. She said Mary Maughan slashed at her neck and face but her scarf protected her until an off-duty garda separated them.

Within five minutes, gardaí arrived and arrested Mary Maughan who admitted her part in the assault and said she had been carrying the knife for her own protection.

The court heard that Teresa Maughan had various tendons in her hands severed when she tried to defend herself. She had surgery under general anaesthetic to get them sown back together.

Mary Maughan had two other convictions related to a dispute with this sister-in-law. She was previously ordered to complete 100 hours of community service for damaging the other woman’s car.

David Costello BL, defending, said Mary Maughan came across her sister-in-law by pure chance on the morning after having been in court and a “red mist descended on her when she saw the person she regards as her nemesis.”

He said she was a productive member of her community and five of her children still lived at home.

The court heard that the women, who are married to brothers, had a good relationship until the last few years and their husbands had kept them apart since this incident.

Judge Martin Nolan said it was a “furious attack” although it seemed to have been a one-off event.

He said although Mary Maughan was a good mother and well-respected and liked by a lot of people, the “savageness and seriousness” of the assault required a custodial sentence.

“I wish I could have been more lenient,” he said.

The judge ordered Mary Maughan to keep the peace and be of good behaviour for two years on her release from jail.