Gareth Lawrence Smither (44) used a combination of knives and a spade to stab and kill Ms Jacobs at her Dunedin home in July 1997 while her 2-year-old daughter, Georgina, was in the next room.
Her battered body was found by her mother, Maureen Watson.
Smither was sentenced to life imprisonment in December 1997.
He was denied parole at a hearing on April 27.
"I don't think he's any better than what he was when he did that to my daughter,'' Mrs Watson said yesterday.
"He's still got the same problems he's had since day one. I don't think he's well enough to be out in the community.''
Her daughter's death had taken a toll on the family and the grief associated with it was an "ongoing'' thing.
"Every time you hear something small on TV it all comes back and in between times you think about your daughter.
"I still don't really sleep at night since this happened to my daughter,'' she said.
Parole decision documents released yesterday said Smither "poses an undue risk to the safety of the community'' and a "moderate risk of both violent and sexual reoffending''.
However, Smither had recently admitted to planning to kill his 26-year-old
ex-girlfriend after their relationship ended.
A clinical psychologist said Smither had made a "significant shift'' in his thinking over the past year and showed a "genuine expression of sympathy'' towards Ms Jacobs.
But a recent psychological assessment report for Smither suggested his risk of violent and sexual recidivism was high, and a decision could not be made on his safe release until he had been "tested over time'' in a "variety of situations''.
Mrs Watson said she always knew Smither had planned to kill her daughter and it was "very strange'' he would only now, nearly 20 years later, admit to planning it.
"That night that he killed my daughter, he rang me and said that he would never kill Karen.
"I can't see why he would say that now when he said in court he never planned to do that.
"I think he's saying that as he has no other avenue to go down,'' she said.
Mrs Watson had been to every parole hearing bar one since Smither was jailed.
"It isn't easy. It brings back all those memories,'' Mrs Watson said.
Smither was previously denied parole in April 2014 for synthetic drug use and "deceitful and dishonest'' behaviour in 2013. He voluntarily remains in hospital care at an undisclosed location.
Smither's next parole hearing would be in or before April 2018.
