She instinctively hit him back, triggering the violent assault in which he punched her at least a dozen times in the face.
Afterwards the bruising to her face completely closed one of her eyes and her face was so swollen it changed her appearance.
Her screams during the assault were heard by Rangi's mother, who came out of the house and told him to stop the attack before walking back inside.
To stop the screaming, he removed his partner's scarf and stuffed it into her mouth, while at the same time blocked her nose.
Unable to overpower him and unable to breathe, she bit his finger. In retaliation he bit her arm, then her cheek.
The bite to her face was done with such force skin was left hanging from her face.
The attack ended and he tried to apologise, but she spent the night sleeping in the car outside the house, before leaving the next morning to drive back to Hastings.
Woman's Refuge spokesperson Kiri Hannifin said many instances of domestic violence went unreported to police and many people got away with it, which was of huge concern to Women's Refuge.
Alcohol and drugs did not cause domestic violence, but could be a "situational factor".
"Raising awareness around it is really, really, important and talking about it - saying that these things are a crime. Be open about who it is happening to and who's perpetrating it," she said.
"In New Zealand we kind of dumb it down and water it down, and the effect of that is we don't take it seriously enough."
Sensible Sentencing Trust spokesperson Garth McVicar said the use of drugs or alcohol was not an excuse for offending.
"There's an opportunity at sentencing for the judge to actually send out a message, not just to the offender, but to the wider community that this type of behaviour won't be tolerated," he said.
"I think he just showed what an absolute coward he is, to continue beating her in the manner that he did."
The woman suffered severe injuries from the attack, including an infected arm, scars to her face and arm from the bites, a cut lip, bloody nose and bruising.
Rangi was remanded in custody to reappear for sentencing on December 12.