As they drove through Takanini, the woman allegedly attacked the constable.
A senior police source told the Herald: "The offender punched her repeatedly about the face and tried to eye gouge her.
"When the attack began her partner quickly pulled over and jumped in to help her."
Counties Manukau district commander Superintendent John Tims said the constable suffered bumps and bruises but no major injuries.
She did not require hospital treatment and was to return to work today.
A woman appeared in the Manukau District Court yesterday charged with refusing to give a blood sample and injuring with intent to injure. She was remanded on bail.
"Police take all assaults against staff seriously," Mr Tims told the Herald. "We are working to support this staff member."
He said attacks on officers were unacceptable.
"Police should not be subjected to any kind of physical violence while in the role of protecting the community."
However, he pointed out that nationally the number of assaults on police had dropped almost 30 per cent since 2006/07.
In line with the national trend, there had been a 24 per cent fall in reported assaults on Counties Manukau police between 2006/07 and 2013/14, Mr Tims said.
"The police take the safety of staff seriously and work very hard to ensure they are well trained, equipped and supported ... In recent years this has included improved tactical training, the introduction of stab-resistant body armour, greater access to tactical options such as Taser and firearms, and the introduction of officer safety alarms for those working in remote areas.
"Tactical training is also heavily focused on officers using their judgment and the de-escalation of violent situations ... This means the vast majority of incidents are resolved peacefully."
Police Association president Greg O'Connor acknowledged that overall assault numbers had dropped, but said serious assaults on police "certainly have not".
"It is no longer an adequate answer for senior police management to give that assaults are dropping when serious assaults are actually rising," he said.