Vic mattock killer says sentence too harsh

A Victorian woman jailed for a decade for fatally stabbing a stranger up to 70 times with a mattock reckons her sentence is too heavy.

Bonnie Sawyer-Thompson, 22, pleaded guilty to defensive homicide and killing 23-year-old Jack Nankervis at her home in June 2014.

In a drug-addled state, she stabbed Mr Nankervis up to 70 times with the gardening tool.

In the Victorian Supreme Court in April, Sawyer-Thompson was jailed for 10 years, with a non-parole period of seven years

She has now sought leave to appeal the sentence, claiming it is manifestly excessive given her young age, guilty plea and the fact she helped police.

Sawyer-Thompson was 19 when she killed Mr Nankervis.

In her Court of Appeal application lodged this month, she said the sentencing judge also erred in finding the crime to be in the upper range of seriousness.

In February, Sawyer-Thompson told police that her abusive boyfriend Phillip Mifsud had ordered her to kill Mr Nankervis.

The court previously heard she did not know Mr Nankervis, but the man was known to Mr Mifsud.

But prosecutor Campbell Thomson said the allegations against Mr Mifsud were false and came 11 months after Mr Nankervis's death.