A woman who threw a knife into her husband's chest and killed him after he arrived home late from work has appealed her nine-year manslaughter sentence.

Katie Anne Castel, 38, killed her husband Jarred Castel, 35, at their house in Chapel Hill, in Brisbane, in 2017.

The couple got into a heated argument when Mr Castel arrived home two hours later than expected.

Mr Castel, who worked in the property industry, was caught up at his office while trying to close a business deal.

Katie Anne Castel, 38, pleaded guilty to the manslaughter of her husband Jarred Castel, 35, who died at their home in Chapel Hill, in Brisbane, in 2017

The couple got into a heated argument after Mr Castel arrived home from work two hours later than expected

Mrs Castel slit her wrists with a 20cm knife before throwing it at her husband while their four-year-old son Levi watched on.

The knife lodged 4cm into Mr Castel's chest and hit his heart.

Mrs Castel, who owned fashion business Adverbium Design, was sentenced to nine years behind bars in 2019.

But she has now lodged an appeal to the Queensland Court of Appeal, claiming her sentence is manifestly excessive.

The stabbing death left the couple's son without parents to look after him.

Mr Castel's father Tony Castel said his daughter-in-law's last ditch appeal is stopping the family from moving on with their lives.

Castel slit her wrists with a 20cm knife before throwing it at her husband Jarred (pictured), while their four-year-old son Levi watched on

'We are totally excluded from the process. Legally, it's got nothing to do with us. It's between the State and her but everything that happens, we're affected. I'm the administrator for the estate,' he told the Courier Mail.

'Our lives are on hold but the bank still wants money and we can't do anything until this is all over.'

In March last year, Mrs Castel sent her former parents-in-law bizarre religious letters from her jail cell.

The letters lasted 12 pages and Mrs Castel touched on religious teachings and her experience of being imprisoned.

'The night I lost Jarred they put me in the Brisbane Watchhouse - it was truly the bowels of hell, a concrete cell with a tiny window I couldn't see out of, graffiti on every inch, no underwear and a couple of plastic-covered cushions,' she wrote.

The mother-of-one went on to claim she was a 'novelty' in jail and she was 'the only one as far as the eye can see who doesn't have a drug charge'.

The letters also told her husband's parents to 'rest in Jesus', and quoted a Bible passage saying: 'He who is forgiven much, loves much'.

Mrs Castel penned a similar letter to Justice Jean Dalton, in an attempt to explain who she is as a person.

'I hope these thoughts will give you some understanding of who I am as a person, how sorry I am and how my husband's death has affected my life,' she wrote.

'I feel deeply the shame of being a prisoner. It is utterly demoralising and demonising to be inherently mistrusted, to have your individuality ignored, and be herded and lined up and counted like livestock every day.'