"I desperately tried to 'pray the gay' away - to be accepted by my family, community and church," she said in a tweet.
"My 'illness' and 'weakness' to temptation was etched as sin into my skin.
"It took a long time to shake that shame and trauma. Tonight our Parliament will ensure this practice is banned in our country for good.
"For our next generation of babies, I am so incredibly relieved. Thank you to everyone that championed this change."
Speaking to reporters on Wednesday, Allan said she was born and raised in a faith-based community within the Pentecostal church. Her parents met as missionaries.
"Being part of the Christian community was everything in the way that I was brought up.
"And so as I began to have these experiences of loving others and in knowing how much the experiences ... were not acceptable to my church and to my community.
"It's such an incredibly hard experience to go through and it lasts for years and years and years as you go through the process of separation.
"First you try to become normal like the others and you reach out to the church leadership and you ask, and they tell you what you're going through is demonic and a consequence of poor choices, that your temptations are sinful.
"When you fail to do that, you fail to live in the life of God. You fail to be one of God's children - it's what you think when you're a young person going through those practices."
After speaking out she said she'd received many messages of support, including from a teacher at her new entrants' school
"She said: 'I love you so so so much, and I'm so so sorry'.
"Because the culture of our church was one that expected these things.
"I don't harbour any negative experiences or ill-feeling towards the people within our community.
"Forgiveness requires understanding and if you understand that people are acting out of a place of love because of a sincere belief, beliefs that have been distorted through whatever ways particular churches have chosen to interpret God's love, well, you can understand.
"People who are in those positions, were doing things out of what they thought was in your best interest because they wanted to pray the gay away for you, so that you might live a life of normality and one that fulfils God's aspirations."
When she was older she turned to the Rātana Church, which she found much more accepting.
There was also still much stigma among Māori communities, which was slowly changing, Allan said.
"Many Māori have lived with now, communities where to be gay is something that hasn't been talked about in the home. I think that there's a lot of a bit of an information gap that we've got to fill collectively.
"But you know, they come from a place of love those questions and queries more often than not has been my experience."
Seeing Parliament pass the bill last night gave her hope for the future, she said.
"I was overwhelmed that we have moved so vastly as a society. So it was a big day for New Zealand and ... did mean a lot to me personally."
It would mean young people, including her own daughter, would "never have to go through the experience of feeling absolutely ashamed of who you are, for who you love", she said.
"And so they never have to go through the experience of being disconnected from the families in the communities of faith.
"That we as a collective Parliament, and therefore its elected representatives of New Zealand, have condemned that type of practice and said that you, whomever you are, are entitled to love whoever you love, and that's a value that we hold dearly, that all of us feel."
The bill, which will come into effect in six months, creates two new criminal offences for either the most serious cases of harm, or where there is a heightened risk of harm. The bill also creates a pathway for civil redress.
Under the bill, it will be an offence to perform conversion practices on a child or young person aged under 18, or on someone with impaired decision-making capacity. Such offences would be subject to up to three years' imprisonment, and up to five years where it has caused serious harm, irrespective of age.
The Attorney-General needs to give consent for those prosecutions.
The bill also provides for civil redress, with complaints able to be made to the Human Rights Commission and the Human Rights Review Tribunal.
Labour promised ahead of the 2020 election to ban conversion practices, and a petition Kerekere launched in February 2021 accumulated 157,764 signatures in a matter of days.
The bill itself received nearly 107,000 public submissions.
