GirlGuiding New Zealand sell biscuits every year during March as part of their fund-raising drive.

Quick-thinking bystanders foiled a crummy crime outside a Hamilton supermarket on Sunday after a woman tried to make off with $400 from a Girl Guides stand.

GirlGuiding "biscuit champion" Glenys Fredericks was selling biscuits outside Hillcrest New World about midday when a woman approached her and asked about the packet prices.

Fredericks, 60, described the woman as "very polite", aged in her 20s or 30s, and well-dressed.

"She came up to me three times asking about the price and on the third occasion said she wanted to buy four packets," Fredericks said.

"I only turned my back for a split second to get the packets when she grabbed the money container and ran off."

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Fredericks estimates about $300 to $400 was inside the container.

"I yelled out and some people gave chase. Apparently she ran to a getaway car across the road and they took off."

Bystanders followed the would-be thief in their cars and recorded the vehicle's licence plate number.

Police contacted Fredericks later that day to say a woman had been arrested and would appear in Hamilton District Court this week.

Some of the money was thrown out of the fleeing car while the remaining cash was apparently recovered by police, Fredericks said.

Fredericks has been selling Girl Guide biscuits for 10 years and said it was the first time anyone had tried to take advantage of her.

She planned to return to her biscuit stand outside Hillcrest New World.

"But I won't do it by myself anymore. It definitely needs two people there.

"It was a bit of a shock afterwards but everyone at the supermarket was very nice to me."