The Yorta Yorta woman, 37, had been transferred to a regular cell after two days on a medical ward.
But her repeated pleas were knocked back by prison guards and healthcare staff.
Ms Nelson, representing herself, had earlier tried to get bail after being arrested for minor offences, but a magistrate rejected her application.
Coroner Simon McGregor on Monday declared Ms Nelson's death in January 2020 was preventable, called for bail law reform and found corrections had failed to provide her with adequate healthcare.
His highly anticipated finding follows a five-week inquest, which ended in May last year.
Ms Nelson was arrested on December 30, 2019, on warrants for breaching bail and suspicion of shoplifting.
She was interviewed by police without a lawyer and represented herself in a bail application, which was denied.
Following dozens of calls for help, Ms Nelson was found dead in her cell at Dame Phyllis Frost Centre on January 2.
She died from complications of Wilkie's syndrome, in a setting of withdrawal from heroin.
Victoria's bail laws are widely considered to be among the toughest in the country.
The state government made changes to the Bail Act in 2018 under expert advice in response to the 2017 Bourke Street massacre.
After pressure from Ms Nelson's family and legal advocates, Attorney-General Jaclyn Symes last week confirmed changes to the laws were being discussed.
Ms Nelson's mother, Aunty Donna Nelson, sat in the front row of the court wearing a possum skin coat and greeted melancholy supporters as she wiped away tears on arrival.
The court room is filled with family and supporters, many from Shepparton and Narrandera in NSW, wearing "Justice for Veronica Marie Nelson" T-shirts and others wearing traditional face paint.
Mr McGregor will continue to hand down his findings, at the Coroners Court in Melbourne.