The woman, who cannot be identified, was arrested in March after she was found next to her submerged car in the presence of her children, all aged under 12.
She was subsequently charged with 11 offences including five counts of attempted murder.
The woman was first refused bail in the Magistrates Court in September but she made a second bid for freedom in the Victorian Supreme Court.
Justice Amanda Fox accepted the woman had exceptional reasons to be released, pointing to an expert opinion that she was mentally impaired.
But she refused her application on Friday morning, finding she posed an unacceptable risk of endangering her children
The woman had told a psychiatrist she did not want to kill her children, instead she had to "save and protect" them from her husband.
She also said she had to kill her youngest child so her husband would love her.
It's alleged the woman locked the doors of her car with the children inside before driving the vehicle off a boat ramp and into a creek on March 1.
She is also accused of forcing her children's heads under water, placing them in danger of death.
The woman had a form of obsessive compulsive disorder and pre- and post-natal depression at the time of the alleged incident, Justice Fox accepted.
But it was unclear how her complex needs would be addressed if she was released back into the community, the judge said.
There were no appointments lined up with a psychiatrist - instead, the woman's lawyer flagged she would attend her GP within 48 hours of her release and obtain a mental health plan.
Justice Fox said that plan did little, if anything, to mitigate the risk the woman posed to her young and extremely vulnerable children.
Because of that lack of structure, the judge said bail had to be refused.
The woman, who appeared on a video link from custody, did not react as the decision was handed down.
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