A woman who killed her four-year-old daughter still believes she was acting on the instructions of God, a court has heard.
Carly Ann Harris, 38, developed a "severe" psychotic illness in the weeks leading up to the killing of Amelia Brooke Harris at their home, Newport Crown Court heard.
Dr Arden Tomison, a forensic consultant psychologist, said that, during his third psychological examination of Harris on November 20, the mother was still firm in the belief that she had to kill her child in order to protect her and save the world.
He said that, despite efforts by doctors at a secure institution to get Harris's psychosis under control, she still believed there had been a "terrible mistake".
"Her emotional level was very much reduced from my first examination," he told the court.
"It was clear that the reality of her situation was becoming more frequent in her thinking.
"She understood where she was and why it was she had been sent to a hospital, but she still felt there had been a terrible mistake and people had misunderstood her.
"She could not understand why she was being subjected to psychological treatment.
"She was still delusional and still suffering from a psychotic illness. She knew that's what people thought but she couldn't quite get that.
"She was very sure she had been instructed by God.
"I am clear in my mind that she was driven to this by her own belief system."
He said that, during an earlier visit, Harris had appeared "at times joyful" and at others displayed "grief at the loss of her child".
Kate Brunner QC, defending, asked Dr Tomison "how mentally ill" Harris was, to which the psychologist answered: "Very. This was a very severe acute illness."
Dr Tomison said he was "as confident as I can reasonably be" that she displayed signs of insanity.
He said he believed Harris developed her mental illness around two months before she killed Amelia, after she told him she was imbued by the spirit of an angel during Passover, which took place between March 30 and April 7 this year.
The court heard that another psychologist, Dr Phillip Joseph, said he believed Harris developed her mental illness two weeks before the killing.
Dr Joseph also said he believed that Harris's abuse of amphetamines may have "triggered" a psychotic episode, which Dr Tomison said was "possible".
But Dr Tomison added: "But I think it's the least likely of the options."
The court previously heard that Harris killed four-year-old Amelia by placing her in a bath of water before deliberately drowning her at their home in Trealaw, Rhondda, South Wales, on June 8 this year.
She then took her daughter's body out of the bath, placed it on a coffee table in the back garden and set fire to it.
When Harris was arrested, she told police: "The angels told me to do it. Just arrest me. It's OK."
Jurors have been given options of deciding whether Harris was not guilty of murder by reason of insanity, or guilty of manslaughter on the grounds of diminished responsibility.
Harris, from Brithweunydd Road, Trealaw, Tonypandy, denies murder and manslaughter.
The trial continues.