A woman who has been "terrorising" her ex-partner for a decade and sent him a threatening "stick figure" illustration is appealing her latest conviction for showing up in his backyard at night.

Kerryn Mitchell, 51, was convicted earlier this year of again breaching the protection order against her ex-boyfriend and his current partner, and was sentenced to two years and nine months in jail.

Mitchell was described by a judge in 2015 as subjecting her victim to "years of relentless offending" following a brief relationship ending in 2006.

A protection order is in place for the victim and his partner, who both have name suppression.

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Mitchell's breaches of the protection order over the years include obsessively harassing the victim with letters from prison, including one with a stick figure drawing so explicit it was taken as a death threat.

Dozens of letters were intercepted but five made it past prison authorities to the victim's address.

Mitchell suffers from post-traumatic stress disorder, as well as alcohol and gambling addictions.

Well known to the courts, Mitchell was the subject of the protection order made in 2008.

"Take the protection order off me and we'll live together happily ever after," she once told the man in a voicemail message.

Mitchell also visited his home about 11.30 one night, armed with a tyre iron, smashing most of the accessible windows in his house.

The most recent offending related to Mitchell showing up to the victim's house at night while he was away on holiday.

She was spotted in the yard on CCTV camera footage. She was also seen on camera trying the handle of the ranch slider door, which Mitchell said she hadn't done.

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She argued she was only there to see her cat.

Mitchell denied a charge of burglary and two counts of breaching a protection order and was found guilty at trial.

Lawyer Chris Tennet said in the High Court at Wellington today Mitchell knew the victim was overseas, but wasn't aware there were house sitters at the property. He said a question needed to be raised over her intent and how that affected the charges.

He argued the burglary charge should only be a breach of protection order, as burglary needed to include an intent to commit an imprisonable offence.

Justice Francis Cooke said showing up "surreptitiously" in the night with a history of offending against the victim suggested there was intent to commit an imprisonable offence.

Tennet also argued the sentence should have been shorter.

Crown lawyer Grant Burston said the Court of Appeal in another of Mitchell's cases described her actions as "terrorising" the victims, and rejected Tennet's argument the sentence was too long.

The 2019 sentence had a starting point of one month higher than a sentence Mitchell received in 2013, which Burston said was appropriate given the ongoing disregard of the protection order.

He also said reports had found Mitchell's mental health issues did not cause the offending, so the sentencing judge was right to not allow a discount on that basis.

"It's no longer extraordinary, there's a different word for it. It's chillingly – it's ruining someone's lives.

"This is about as bad as it gets."

The judge will reserve his decision.