She told the costume store manager she was playing a trick on her boyfriend - who had been away for a while - and wanted to look a few months pregnant.
Nadene Faye Manukau-Togiavalu continued to hire the fake pregnancy suit on a weekly basis, increasing the size of the costume to fit her maintain the charade.
Her lie - like the fake baby bump - grew, and her story changed. She explained to the manager she was now in a play with the role of a pregnant woman.
These details, revealed in court documents obtained by the Herald on Sunday, led to the 21-year-old kidnapping a newborn baby from her cot. They can finally be revealed after she was jailed for three years last week.
Much of Manukau-Togiavalu's offending may have stemmed from the killing of her cousin - rising rugby league star Luke Tipene.
Tipene died after he was stabbed in the neck with a broken beer bottle by Vincent Skeen during a brawl outside a party in central Auckland in November 2014.
Manukau-Togiavalu held her 17-year-old cousin in her arms as he bled to death.
She later gave evidence at Skeen's murder trial and retrial, when he was convicted of manslaughter.
"He was my little cousin and I was supposed to look after him," she testified.
Since then, she has suffered from delusions, post-traumatic stress disorder and even created an imaginary friend, according to a psychologist's report.
Her offending began with the pursuit of attention from a teenage boy.
In early 2016, she asked the teen, with whom she had been friends for years, if she could move into his family home as she had issues with her own family.
The teen, whose identity is suppressed, and his family agreed to let her stay for a couple of weeks.
But that turned into months, and Manukau-Togiavalu continued to give excuses for why she needed to stay.
In November 2016, the teen's family grew concerned over his mental wellbeing when the pair began a casual relationship and they asked her to leave.
Manukau-Togiavalu moved out, but began a meticulous campaign of harassment.
In December 2016, she contacted the teen online and told the first of many lies - she was pregnant with his child. She also convinced her own family she was having a boy.
She started following him during his daily routine and tracking his social media activities.
Manukau-Togiavalu persuaded friends to drive her past his house and on occasions would hide in the bushes near his home.
He blocked her from his social media profiles and refused to answer her calls.
But while they were together Manukau-Togiavalu had collated nude photos and videos of him, most taken without his knowledge while he was showering or getting dressed.
She posted them on social media and his family sought the help of Netsafe to remove the images.
In March last year, Manukau-Togiavalu went to a costume hire store in Avondale and hired a four-to-five-month-pregnancy suit.
During that time, the store asked her to return a five-to-seven-month-pregnancy suit.
She said she'd left it in a bag at the store but security footage showed otherwise. Manukau-Togiavalu then stopped all contact with the shop.
In May 2017, she contacted her ex-boyfriend at work and provided a false name, Annalise Wilson.
She made a fictitious complaint, claiming he was tailgating her in a company car and driving recklessly. She passed on staged photos to his manager and he received a formal warning.
She said to a friend: "Wouldn't it be funny if he lost his job."
She also turned up to her ex's workplace and was served two trespass notices.
However, the next day, in July, she went to the Waitākere District Court to get a protection order against him.
In her affidavit she claims he threatened to kill her, was beating her, stalking her on social media, and following her in person.
"I am constantly worried for the safety of my unborn child and myself," Manukau-Togiavalu wrote.
"His short temper causes him to make erratic decisions and I am always uncertain of what he may do.
"He tracked me down where I live without any knowledge and I fear he may harm myself, my family members or my unborn child."
But the next day she cancelled the application - explaining it would all be too stressful while she was carrying a child.
Manukau-Togiavalu's infatuation with pregnancy then led to her applying to be a nanny for newborns.
Her soon-to-be co-defendant and cousin, Sydnee Taulapapa, provided a glowing reference.
She told Taulapapa a different lie - that she had given birth and had the baby adopted out, but that she'd made a mistake and now wanted it back.
Manukau-Togiavalu used Taulapapa's email to say she had previous experience caring for babies and had cared for Taulapapa's fictitious children.
The agency, which has its name suppressed, offered Manukau-Togiavalu jobs caring for older children, but she declined - she was specifically after a newborn.
In late July she accepted a position looking after a baby due in early August for an Epsom family.
But she did not continue her fake pregnancy lie around them or her new employer.
When she first met the baby's mother, Manukau-Togiavalu told her she had given birth to two baby boys, but that one of them had died.
Manukau-Togiavalu had in fact been pregnant earlier in her life, but had an abortion.
She also told the mother, at Middlemore hospital after she'd given birth, that security was tight because a baby had been stolen and was yet to be recovered.
She quickly had to amend her fake pregnancy story to her own family when she discovered her new employers were having a girl.
Taulapapa arrived from Australia in mid-July and the pair began their plan to kidnap the family's child.
When later interviewed later by police, Taulapapa said she had been coaxed into helping steal the baby, whom Manukau-Togiavalu claimed had been adopted out to for $19,000.
But Manukau-Togiavalu's plan all along was to snatch the baby and pretend it was hers and the father her ex.
Born in late July, the baby was cared for by Manukau-Togiavalu overnight at the Epsom family's home two to three times a week.
By August, she had hosted a baby shower and her room was adorned with baby products, including a cot.
On the evening of August 8, Manukau-Togiavalu asked the baby's mother if their family dog barked - a sign she was finalising her plans.
Taulapapa told Manukau-Togiavalu's family she had just taken her cousin to the hospital to give birth.
At about 11.30pm, Taulapapa waited in Manukau-Togiavalu's car near the Epsom home and in the early hours of August 9, the baby was taken.
CCTV footage, described by the father as a "like a horror show", shows Taulapapa creeping into the home through the back door wearing a balaclava.
As Taulapapa tiptoed towards the front of the property - the baby girl in her arms - Manukau-Togiavalu opened the electronic gate from inside the house to let her cousin out and the 11-day-old girl was gone.
Manukau-Togiavalu then had a shower before she told the parents their baby had been stolen.
"The house has been robbed. The house has been robbed," the baby's father recalled hearing her yell.
"In my heart I knew straight away something was wrong and Nadene was not telling the truth," he said.
"Where's our baby, Nadene?"
The parents and about 80 police launched a major search to find the newborn.
At about 1.15pm, Taulapapa was located in Manukau-Togiavalu's Suzuki Swift in the suburb of Favona.
Next to her was the baby.
Taulapapa was discharged without conviction, ordered to complete 400 hours' community work and pay $2000 to the baby's parents or to a children's charity over the kidnapping.
However, the Solicitor-General is appealing that sentence.
When interviewed by police, Manukau-Togiavalu denied any knowledge of the kidnapping.
But when police told her the baby had been found, her lies stopped.