A nurse suspended for tampering with COVID-19 vaccines told a pharmacist she was only checking they had the correct dose.

It formed part of the unprofessional conduct and implausible claims that led to the nurse and midwife's three-month suspension, and the rejection of her evidence about the tampered vaccines.

Kylie Sharee Parmenter was caught out when she returned to the same regional NSW pharmacy where she had earlier replaced vaccines meant for herself and a close family member during one of the state's COVID-19 vaccination drives.

The nurse and midwife was found guilty of professional misconduct on Tuesday and ordered to undergo counselling by the NSW Civil and Administrative Tribunal following action by the Health Care Complaints Commission.

"For completeness we also find that practitioner's behaviour was also objectively unethical," the tribunal decision said.

Ms Parmenter went on leave at the end of September 2021, when health care staff had been ordered to receive their first COVID-19 vaccination to continue working.

She tried to get a vaccine that day at a Griffith pharmacy, inspecting a consulting room before booking an appointment for two days later.

Despite being on leave at the time, Ms Parmenter wore her NSW Health nursing uniform with a long-sleeve short underneath to the appointment on October 2, 2021.

"(I was) thinking if I walked in there with my work uniform on they'd be less suspecting of me," she later said.

Ms Parmenter replaced the vaccines in two syringes with another liquid in the 95 seconds she spent alone after asking a pharmacist and her relative to leave the room so she could remove her long-sleeve shirt.

She returned to the pharmacy with the family member four weeks later, ostensibly for a second vaccination.

Ms Parmenter again wore her nurse's uniform despite being on leave and asked for privacy, raising a pharmacist's suspicions.

They looked at the CCTV footage, believing that the woman was tampering with the vaccines.

One of the pharmacy's owners then confronted Ms Parmenter in the consulting room.

"I am making sure you're giving the correct dose to us," the nurse responded.

Ms Parmenter later told the pharmacist she was "just trying to dilute the vaccine" to make it gentler on her relative.

After apologising, the nurse and her relative were given genuine doses.

The tribunal did not accept Ms Parmenter as a credible witness unless her testimony was supported by others due to inconsistencies in her evidence, implausible holes in her memory and lies she told police.

Asked why she had waited until the end of a six-month period while eligible to be vaccinated as a health-care worker, Ms Parmenter said among other reasons that transmission rates for the virus were lower in the summer months.

"Patently, March to September is not 'over the summer months'," the tribunal said.