She shut the door to the room and listened out in case the baby cried.
"I got out of the shower and the crib was empty ... I knew right away something was wrong," she said.
"Then the night nurse came in and I asked her if the baby had been crying. I thought she must have taken her. She said no, she was just there to introduce herself. We thought another nurse must have come in."
After checking with other staff, Mrs Pretorius came to the horrifying realisation that her 5-day-old had been abducted.
"I thought I was going to die ... It was so scary. It was terrifying. I thought if they didn't find her soon I would rather jump off a building than carry on. I didn't want to live any more if something happened to her."
Police converged on the hospital and the hunt for the kidnapper began.
Eight hours later, Mrs Pretorius' husband woke her with the news from the police that Nadine had been found.
Mrs Pretorius has a strong Christian faith and had been praying through the night for her daughter - and for the person who took her.
"I just had to trust God that she would be OK. And the police did such a good job."
She recalled the moment police handed Nadine back to her.
"The moment I got her in my arms, she went straight to my breast [to feed]. It was like she didn't even know she had been away."
A 31-year-old man and a 26-year-old woman have been jointly charged with kidnapping Nadine.
Mrs Pretorius had not given them much thought. But she did want to acknowledge that they looked after Nadine. "She was fed, she was cared for. I'd like to think they cuddled her. I think she would have cried for me ... but I don't want to think too much about that," she said.
Back at her South Auckland home last night, Nadine cooed and gurgled next to her mother. "Every cuddle, every hug, every little kiss, means so much more now," Mrs Pretorius said.
She said she and her family would have counselling next week, but this weekend they just wanted to be together - and sleep. "We've had no sleep, so that would be good."
The family's pastor, Andrew Bergh, spent Thursday night with Mrs Pretorius and her husband, praying with them for Nadine's safe return.
"The hardest thing for any mum is for her little baby to be taken," he said. "[Mrs Pretorius'] amazing faith allowed her to walk through that anxiety and not blame that woman. In fact, she prayed for the lady [the alleged kidnapper]."
Nadine is the second baby in recent years to be taken from Middlemore Hospital. In 2012, a newborn was also taken from her crib.
Yesterday, hospital services director Phillip Balmer was concerned that beefed-up security installed after that incident was not enough to stop Thursday's abduction.
Further interim measures were implemented yesterday, pending a full investigation.
The pair accused of kidnapping Nadine appeared in the Manukau District Court yesterday.
Faatiga Joe Manutui was given bail but the woman, who was granted interim name suppression, was remanded in custody.
The court ordered a report into her mental health.
