In the previous letter also obtained by ABC News, Elisa Baker, 42, maintained neither she nor her husband killed Zahra, but that the father did something "horrifying" after the girl was dead. In the new letter, she said she is working with police to get him locked up "for [her] safety."
"My family will never believe Adam has done what he has," the letter says. "I am helping the cops try and get my soon-to-be ex-husband in here. The cops promised if I would help them with what I know, they would keep him locked up for my safety... I was trying to save us both, but why should I? He is letting everyone destroy me."
Adam Baker, 33, is currently free on bail after he was arrested on unrelated charges last month.
Mark Killian, an attorney for Adam Baker, said news of the letter is just another painful hit for the man who learned his daughter was dead on Friday.
"These accusations are... I don't know know what to say," Killian told ABC News. "Mr. Baker obviously categorically denies any of this.... We just see these writings as desperate attempts of someone incarcerated to divert attention away."
Killian said Adam Baker took news of his daughter's death as "shock... just the worst nightmare."
In the letter Elisa said she feels like a "freak in a carnival" whenever she's in view of the media's cameras and is concerned about being attacked while in prison.
"[But it's] not like I am not able to defend my freaking self," she writes.
The letter is signed, "Dark Wishes, Elesa." She claims in the letter she had changed her name from Elisa to Elesa.
Zahra Baker's Australian biological mother said Sunday she is trying to believe the girl's father was not involved in her death.
"I have to take a step back and think of the possibility that maybe Adam [Baker] wasn't involved and maybe he is hurting as well," Emily Dietrich told the Australia-based Seven Network.
Dietrich, who lives in Wagga Wagga, New South Wales, Australia, had given Baker custody of Zahra when she suffered post-natal depression. She told the television station she hadn't seen her daughter since the girl was 8 months old and didn't now that Baker had taken her to the United States until days before she was reported missing, Oct. 9.
"I can't explain the anger, the hurt," she said. "He had no right to do any of it, to keep her from me."
The girl's remains were discovered last week during a search in Caldwell County, N.C., where the Baker family previously lived.
Zahra was reported missing by her stepmother and father on Oct. 9, but police say no one outside of the family has reported seeing her since Sept. 25.
The girl had a grueling life. Stricken with bone cancer, she lost her left leg and much of her hearing. Relatives and neighbors said that Elisa Baker, was abusive to Zahra, who was often bruised.
ABC News' Yunji de Nies and Dean Schabner contributed to this report.