A friend of a woman charged with attempted murder says her mate showed her photos on a phone of the victim's face bruised after a bashing.

Nicola Jones and Julie-Ann Torrance are accused of attempting to murder the now 20-year-old victim, who was found dumped and critically hurt near State Highway 1 north of Auckland in May, 2016.

Wayne Blackett has pleaded guilty to the attempted murder charge.

Jones and Torrance are also charged, alongside Cameron Hakeke, of kidnapping, aggravated robbery and assaulting the same victim with a taser in a separate attack on April 23.

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On Thursday at the High Court at Auckland, Maria Rollo said her friend Jones had complained in early 2016 that the victim had slept with her partner of 12 years and caused the end of their relationship.

Jones said she was going to make the victim pay, Ms Rollo said.

She said after one weekend Jones spent in Auckland, she returned and showed Ms Rollo photos on her phone of the victim with bruises all over her face and a shaved head.

Ms Rollo said Jones had told her the victim had been tied to a chair, given a "hiding", had her hair shaved and been forced to sign her car over into another person's name.

Jones, Torrance, Black and Michelle Blom are accused of targeting the victim again shortly after the first attack.

Prosecutors say they pulled the victim off a central Auckland road and subjected her to a long attack in a basement on Great North Road, including cutting her hair, breaking her fingers and sexually violating her.

Jones, Torrance and Black then drove the victim to the Dome Valley, where they bashed her head at least seven times with a hammer and left her to die on a dirt road just off State Highway 1, prosecutors say.

The trial continues.

- AAP