Prue will watch from the public gallery this evening as Ms Wall gives the first speech on her bill, which is expected to pass into law with strong support.
The genesis of the legislation came from the most unlikely place - the rugby fields of Hamilton.
This was where Ms Wall first found a proud lesbian, gay, transgender and bisexual community and the encouragement to come out as gay herself.
"There were out, proud members of the rugby team I played with. I guess we had a critical mass of [gay] women in the rugby scene."
She said she had been too distracted by netball at high school - she was New Zealand's youngest-ever Silver Fern - to question her sexuality, but began to feel she might be gay at age 19.
When she was 21, Ms Wall found a partner and came out to her parents. Compared to the "horrific" stories she had heard from submitters on her Marriage Amendment Bill, she said that this step was relatively easy.
"When I knew who I was ... I told my parents and they accepted who I was and said they loved me and that was it."
After she "drifted apart" from her partner of 10 years, she met Prue while working at the Waiatarau Branch of the Maori Women's Welfare League.
Ms Wall entered Parliament in 2008, and when she was given the Rainbow Affairs portfolio for her party, she felt it was a natural next step to draft a bill to legalise gay marriage.
The bill would allow same-sex couples to adopt children.
Ms Wall said that having children was not a possibility for her: "I did want to be a mother, but it just didn't work out for me."
Green MP Kevin Hague, who is gay, said at the beginning of the debate he had not planned to marry his long-time partner.
But he admitted that he could be warming to the idea: "I don't know now. But it wouldn't surprise me if we do."
