Ms Ostick approached the woman and asked her why she used the beach as a toilet.
The woman told her she didn't care. "It's not the first time and it won't be the last," the woman said.
The woman's husband, who said they were from Cromwell in the South Island, told Ms Ostick to "go back where you came from, we were here long before you".
Ms Ostick, who is Maori and has a ta moko on her chin, clearly did not arrive in New Zealand last week.
Later that day she posted photos of the couple and their vehicle on a Facebook page called the Paihia Noticeboard. The post has been widely viewed and had attracted more than 120 comments within first 24 hours.
Ms Ostick said she picked up rubbish from the beach most mornings and regularly told off freedom campers for hanging clothes in, or leaving food scraps around, a tapu tree next to Waitangi Marae.
This summer had been worse than usual for visitor behaviour, she said.
A day before the beach peeing incident a man hopped out of his van and left a bag of rubbish outside her gate. She had stopped running the track to Haruru Falls because of the amount of toilet paper and human waste visitors left behind.
A Far North District Council spokesman said the council could lodge a complaint about the toileting woman with police, who could then issue a warning or prosecute her for indecent exposure as long as eyewitnesses were willing to give evidence in court.
The council could also issue a $400 fine under its Litter Infringement Policy, but that would depend on whether the woman defecated or urinated on the beach.
From Easter the council is replacing its one-size-fits-all $400 littering fine with a schedule of fines ranging from $100 for a small amounts of litter up to $400 for repeat offences and offensive waste. The council can also prosecute in serious cases.
