Heather Arnold, 59, was found guilty in 1987 of murdering Jeanne Sutcliffe and her eight-month-old daughter in Westbury, Wiltshire.
At the trial she said she knew nothing of the killings. But she later admitted to psychiatrists that she "hated" Mrs Sutcliffe and had killed her because she wanted to be closer to Mrs Sutcliffe's husband, Paul, a fellow mathematics teacher.
A consultant psychiatrist at Broadmoor Hospital said in 1993 that Arnold should appeal against conviction on the grounds of diminished responsibility. Yesterday the Appeal Court was asked to either substitute verdicts of "not guilty of murder, guilty of manslaughter by reason of diminished responsibility", or order a retrial.
But Lord Justice Hobhouse, giving judgment with Mr Justice Laws and Mr Justice Butterfield, dismissed the appeal. "She has failed to persuade us that it is necessary or expedient ... to admit any further evidence," the appeal judges said.
The judge said that before her trial Arnold was subjected to psychological tests and "no relevant abnormality was found".
She was shown to be highly intelligent and although the defence of diminished responsibility was available at the trial, the defence did not use it. "She was an intelligent and articulate woman. She was in a fit state to take decisions about her defence and to instruct her lawyers."
During treatment for depression at Ravenscroft, Arnold began to give accounts of what had happened which "varied markedly from what she had said at the time of the trial", Lord Justice Hobhouse said.Reuse content