Rosie Batty says the opportunity for intervention would have been a key factor in saving her son, Luke.
Her comments come as the new prime minister is set to announce a $41 million-plus domestic violence package in Melbourne to increase and improve support services for women.
Ms Batty, who was named this year's Australian of the Year, has been pushing for more funding and education to tackle the problem since her 11-year-old son was killed by his father.
She said the funding would bring greater awareness to the problem, but said the lack of intervention available to people suffering mental illness is disappointing.
"What I really regret is that Greg (Luke's father) didn't get the opportunity to have serous mental health intervention," Ms Batty told ABC Radio on Thursday.
"Although it wasn't just his mental illness to cause him to do what he did, I think that would have really helped and very definitely, I don't think that Luke would have died."
The government-funded package will include $36.5 million over three years to train front-line employees, including police, social and community workers and medical staff.
Ms Batty said the systems and processes are what let families affected by domestic violence down.
"The process is that we work very much in silo," she said. "What we do need to see is greater collaboration.
"It is not necessarily the individuals that let you down, it is quite often the systems and processes and we really do need to improve our responses to perpetrators and have greater accountability and effective intervention."
At least one woman is killed each week by a partner or ex-partner, yet recent media reports suggest the number is a lot higher.
