Having been arrested on a non-violent traffic offence carrying a mandatory imprisonment term, there was nothing she could access in the way of counselling, rehabilitation or mental health support.
"People think prison is where rehabilitation happens but it is so overcrowded, you wait for a really long time to get into courses, if there are any available to you," Ms St Clair told AAP.
"I was dealing with addiction, domestic violence and trauma and I look back now and realise I was a young girl who didn't know how to grieve and just slipped through the cracks.
"Jailing people is failing people, especially women, and we need to think about trialling other things."
Indigenous women are significantly over represented in the criminal justice system and facing the highest rates of imprisonment recorded since 2014.
The imprisonment rate of Aboriginal women is 22 times that of non-Indigenous women, and most are mothers who could have been safely diverted from prison, according to the Keeping Women Out Of Prison (KWOOP) Coalition.
A remand crisis reaching critical levels is being blamed for the increase in imprisonment rates, with more than 60 per cent of women in NSW prison held while they await trial.
More than half ultimately do not receive jail time as most are charged with minor offences.
It costs the state $180,000 per woman per year in prison, plus $110,000 per child per year in out-of-home care.
What changed the trajectory of Ms St Clair's life was not the prison system, but support she found through Success Works, which helps women impacted by the justice system to access meaningful jobs and overcome employment barriers.
Ms St Clair was assigned a mentor through the program, who she says has been one of the biggest supports in ensuring she could gain and sustain employment.
"Having someone believe in me before I believed in myself has been such a powerful thing," she said.
"Having financial independence has meant I can support myself and my son, it's helped my mental health and given me a sense of purpose."
The KWOOP Coalition is calling on the state government to substantially increase investment in evidence-based diversion programs.
Research consistently shows these programs deliver better outcomes for women, children, and communities and offer a clear alternative to incarceration for women facing minor charges and remand detention.
The state was spending more than $200 million a year to imprison women, most of whom are on remand or face short sentences, KWOOP co-chair Eileen Baldry said.
"Because the drivers of their offending are not addressed, prison is a very expensive revolving door," she said.
"This is not a funding problem, it is a political will problem.
"The solutions exist, the programs work (and) what we need now is the decision to invest."
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