The conversation got deeper as they got to know each other and over the years they shared in each other's lives through all the ups and downs.
"I think there were no limits like there were with other friends," Mrs Carlsson said, "You could talk about everything."
They often talked about boys they met, and followed each other through dating, marriage and families.
Mrs Carlsson remembered Mrs Woods writing from New Zealand to say she was engaged and later when she had her first child. Mrs Woods recalled getting a photo of Mrs Carlsson pregnant in Sweden with her first daughter.
As their families expanded the letters became fewer and further between but they never left it longer than six months without writing.
"When we got families it was a letter for Christmas and updates on families and photos," Mrs Carlsson said.
Mrs Woods agreed: "We kept up with the babies, our lives, the ups and downs."
They shared photos and gifts from their countries and dreamed of meeting.
Mrs Carlsson said: "52 years ago it was like taking a boat and a couple of months' time.
"My parents said 'not a chance, we can't afford to take you to New Zealand'."
The letters continued and now, at age 63 and together on the couch, they said they could not imagine life without having shared it all with the other.
"It's a part in the heart," Mrs Carlsson said. "I feel a little part Kiwi."
At the airport I was totally overwhelmed. I didn't know whether to cry or what. I was just shaking.
Five years ago they transitioned to email and later to Facebook, which allowed for more photo sharing and meant they could talk more often. They had spoken on the phone twice, some years ago, but the strong accents made understanding each other difficult.
"I was very nervous we wouldn't be able to talk, but communication has not been a problem. We understand each other completely," Mrs Carlsson said, her husband Peo Seensson agreeing there had not been a quiet moment since they arrived.
"Every now and then I think, 'is this really happening?'," Mrs Woods said. "At the airport I was totally overwhelmed. I didn't know whether to cry or what. I was just shaking."
Mrs Carlsson laughed: "I didn't know you were so short"
Mrs Woods showed Mrs Carlsson around over the long weekend before the Swedes headed south to explore New Zealand. They will reunite for two days next weekend before the Carlssons head home.
"Now we're trying to get Annette to Sweden," Mrs Carlsson said.