She also told workmates that she would not leave her alcoholic husband, who she accuses of beating her up regularly, because she was worried about losing her share in the house.
Mrs Thornton, 41, denies murdering Malcolm Thornton and says that she stabbed him accidentally after a row. She is being tried for a second time after the Court of Appeal ordered a retrial.
In court yesterday, former colleagues at the company where she worked in Atherstone, Warwickshire, alleged that in the period just before the stabbing in June 1989, Mrs Thornton threatened to kill her husband on a number of occasions.
One of them, Helen Thomas, said: "Three days before the killing she said that she wasn't happy with the way things were and that she would have to get rid of Malcolm and have to kill him. It was just the way she said it ... it did scare me.
"She said she was going to have to get a knife and kill him. I can remember the exact words. She did not seem angry."
After killing her husband, Mrs Thornton is said to have telephoned Mrs Thomas. "She said, 'I have done what I said I was going to do'. She said that she felt she had got to and she did not feel guilty."
Mrs Thomas said that on one occasion she had advised Mrs Thornton to leave her husband. "She just said that she loved Malcolm and she would not leave him ... she was not going to give up her house, her home and everything that she had got."
Susan Davies, another workmate, told of a separate conversation."She did say that if she did anything to him, 'I won't go down, they know what he is like.'
"I assumed that her claims of him having beaten her had been recorded. She said that if she left him, she would lose her part of the house."
A third colleague, Sally Harper, said that the day before the stabbing she overheard a telephone conversation at work between Mrs Thornton and a bank manager, in which the accused woman allegedly said: "He will be dead soon; he will be dead soon."
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