A woman who followed her former husband's partner after choir practice and assaulted the woman in a car has lost an appeal against convictions for threatening to kill and attempted kidnapping.

Court documents show that after the woman got into her car after choir practice to drive home, a person opened a rear door, climbed into the back seat, grabbed her by the hair and pulled her back violently, telling here to "shut up and drive".

The force caused a cut to the woman's lip. The assailant looked her victim in the eyes and asked her whether she wanted to "die now or later".

The woman managed to break free, got out of the front door and yelled for help, says the Court of Appeal judgment, given by Justice Raynor Asher.

Cornelia Thornton was charged with breaching a protection order, threatening to kill and attempted kidnapping. She was convicted in the Tauranga District Court and sentenced to two years and 10 months' imprisonment.

The documents said after the husband and Thornton separated, the husband moved into the woman's house.

"There was then a history of Ms Thornton antagonising her former husband, which led to a number of convictions.

"The former husband had obtained a protection order against Ms Thornton. The order was made permanent in January 2015, and the complainant was added as a protected person in April of that year, some seven months prior to the attempted kidnapping," the document said.

Thornton's appeal was based on four alleged errors by the district court judge - wrongful admission of seven previous convictions relating to her former husband; a statement by a police sergeant who interviewed her on the day of the offence; identification evidence and the judge's summing up.

"The grounds of appeal have not been made out, indeed none of them had any significant merit," the judgment said.