John Cooper, QC, mitigating, said she was a woman in crisis and had not been given the help she asked for.
But the Recorder of London Judge Brian Barker said Edgington should stop blaming others for her actions and take responsibility.
He jailed her for life with a minimum term of 37 years for murder and gave her a concurrent sentence of life with a minimum term of 20 years for attempted murder.
Judge Barker told 32 year old Edgington that her behaviour had been "consistent and calculated".
He said: "You are manipulative and exceptionally dangerous. What you did could not have been more selfish. I disagree that the responsibility for these acts can be laid on others. You made your choice and these were terrible acts for which you must take responsibility.
You have come as near as can be to having three deaths on your hands."
Miss Clark had escaped only with cuts to her hands because of her bravery and quick action, he said.