Also she had no brothers so got stuck with the labour-intensive family farm duties such as milking.
The institute was a way of escaping this duty and getting stuck into some gardening - one of Mrs O'Brien's favourite activities.
One of the intentions of the institute was to give rural women more of a voice in the community.
"It gave country women the confidence to run meetings," Mrs O'Brien said.
But the activity at the institute went much further than that.
"I got roped into acting. We did concerts, we did a three-act play."
In the early '40s the aim of these performances and various other community activities was to generate some money for New Zealand soldiers overseas.
Mrs O'Brien said the morals of the institute have remained pretty consistent, but the days of the long drives into town in the family's model T ford are long gone.
One of the biggest differences between then and now was having no electricity in the hall in Tinui.
"We had to heat the copper for hot water, we had to supply the wood to heat it."
In the 1950s the Memorial Hall in Tinui was built as new accommodation for the Women's Institute.
In that era major fundraising efforts through concerts and performance were put on at the new hall to raise money for returning service men.
In 1963 Mrs O'Brien sold her 900 acre farm in Tinui to her son in law to come and live in Masterton.
But doing nothing has never been an option for her - in 1998 she bought a 22 acre farm.
"One hundred ewes to keep me going," she said.
She is the oldest surviving member of Women's Institutes in the Tinui/ Whareama area.
The secret - "I don't drink, I don't smoke and I went horse riding."
She said she hasn't been horse riding since she was in her seventies, in a tone of voice suggesting that this isn't a very good effort.
Mrs O'Brien said the institute has meant everything to her over the years, she still drives to Tinui "un-announced" to ensure everything is running smoothly.
"They are more than friends, it is like a big family."
