Despite not running since her knee reconstruction surgery in January, she followed her out of the shop door, catching the attention of bystanders in the process.
"I actually thought I had stood still for what seemed like ages, but watching the footage I actually took off straight away. She did not run, she marched out walking very fast. Once I alerted everybody, then she started to run. I was just yelling 'stop that girl, she's stolen a ring', people must have been looking at me like I was a fruit loop."
Mrs Blatch said yesterday she still had "Benny Hill music playing" in her head.
As the pursuit began, some men in overalls, nearby shop employees and a staff member from the New Zealand National Aquarium joined in.
"I lost sight of her once I got up to the Soundshell, I was way behind her," Mrs Blatch said.
Matt Gowan was just finishing his lunch break and heading back to the Aquarium when he spotted the action.
"I picked up the chase from outside Hannahs shoe store," he said.
"She ran up out through the Soundshell and down to the beach. She knew I was catching her so she tried to throw the ring - it did not go far, maybe eight or 10 feet."
The woman's attempt to throw the ring into the surf failed, so he picked it up and kept following her.
"She was pretty quick. I was sort of gaining on her, but I think she could hear me on my cellphone gasping and trying to talk to police at the same time."
She went back down Tennyson St, before turning onto Cathedral Lane but was nowhere to be seen when he turned the corner.
"The main thing was I had the ring in my hand," Mr Gowan said.
Police arrived on the scene only minutes later. The woman was not found, but the ring was returned to the shop.
"It just gives reassurance that there are heaps of really good people around, that give great support, and we're really, really grateful.
"They all need to be thanked individually - I just don't know who they are," Mrs Blatch said.
