He had spotted her distinctively shaped eyebrows, and assumed she was a Dresden Dolls fan.
Palmer told him she would be attending - without revealing who she was - just to see what he had to say.
"I always do this to people," she blogged afterwards.
"I get the feeling that I might learn secret information if I pretend to be a fan."
He didn't identify himself; she didn't identify herself.
"We were talking, then there was this sense of mutual confusion, then we found out who each other was," she told the Herald on Sunday yesterday.
"It was sheer, bizarre coincidence that I ran into him."
Fan Roger Grauwmeijer said a buzz went through the crowd when Palmer introduced a "very special guest".
"They brought Richard out and everyone went crazy. They just loved it."
After the number, UK-born O'Brien, 68, thanked the audience for his New Zealand permanent residency, granted in 2010 after the intervention of MP Kate Wilkinson.
Usually an applicant has to be under 55 years old.