The court heard that many of the people who unwittingly gave her money were from overseas, or spoke limited English.
The 50-year-old ex-admin worker has since left the Canterbury DHB after being caught fiddling the system in 2019.
The CDHB's acting chief executive, Dr Andrew Brant, said after sentencing he was "extremely disappointed" that a former staff member had been charged with false accounting.
"When employed by the DHB, the staff member was responsible for liaising with individuals and at times their insurance companies to arrange payment for healthcare services provided to people in Canterbury who are not eligible to receive publicly funded healthcare."
When concerns were first raised, he said, the DHB's internal audit team found indications of fraudulent activity.
Preez was suspended, police notified, and a third party began an investigation.
It was recommended the DHB improved its internal controls for managing revenue from patients who were not eligible for healthcare services in New Zealand.
"A number of changes" were made, said Brant.
"We have ensured that no patients are out of pocket as a result of the individual's actions, and we are working with our insurers regarding the loss incurred by the DHB."