However she did not accept Deo's defence that her inexperience and lack of training led to her actions.
"The victim was clearly an elderly vulnerable man who required the utmost care regardless of the stage of his illness."
She said the fact Hemi did nothing to assist Deo as she tried to dress him in his bed may have explained the assault but did not excuse it.
Judge Saunders said a conviction would not prevent Deo from being accepted to Wintec to train as a nurse, or receiving Nursing Council registration. It was up to those institutions to decide.
The court heard that Deo's sister was a nurse and it was a career she aspired to.
Police opposed the application to discharge Deo without conviction, which meant she would not need to disclose the assault that she earlier pleaded guilty to when applying to study or for jobs.
Judge Saunders described the offending as moderately serious.
"He was alone. He was under your care. He was clearly vulnerable and totally reliant on you.
"Ultimately you don't need to be a registered nurse to understand that it is simply unacceptable to hit a patient in any way, shape or form."
She convicted Deo and discharged her without penalty.
Outside the court, Deo walked quickly away from media without comment.
Hemi's son and daughter-in-law Allan and Priscilla Hemi said they were pleased Deo was convicted and hoped it never happened to anyone else's family.
Allan Hemi said his father was psychologically traumatised by the assault.
"He used to cower in the shower and say 'Don't hit me, I'm dumb'."
The family took Hemi out of the rest home to live with them and said his happy personality returned before he died, aged 87, on January 5.