She also began screaming and was heard by her neighbours.
They spotted a man in their shared driveway and - noticing he was acting suspiciously - followed him to a house about 1km away.
A 39-year-old man was arrested shortly afterwards.
Police praised the neighbours and said their actions should be highly commended.
Last night, they were reluctant to speak about the incident, saying police had told them not to comment.
Another neighbour applauded their efforts.
"They did a great job," he said.
He was awakened by police later in the morning when they door-knocked the street as part of their investigation.
The man has a security system set up at his house with cameras, and he has given the footage to detectives.
The woman who was assaulted lives alone down a shared driveway and knows her neighbours well.
"She forgot to lock the door. She's doing okay, she's just shaken," the neighbour told the Herald.
Residents in the street were shocked by the attack.
"I thought it was a good street. That's bad," said one woman.
A man said: "It's quite a safe street. I've been here 13 years and this is the first time something like this has happened. It's terrible."
The 39-year-old has been charged with burglary and intent to commit sexual violation and is expected in the Manukau District Court today.
Inspector Jim Gallagher said the emotional impact of the attack on the woman was "hugely significant".
"The elderly in our community [are] a vulnerable group, just as children are, and they need to be regarded as such."
Age Concern has urged older people to "never let their guard down".
How to stay safe
* Don't try to catch an intruder or block their escape.
* Lock all doors and windows before you go to bed.
* Get to know your neighbours.
* If you have a medical emergency alert, keep it close.
* If you live alone, don't advertise the fact.
