Anne Darwin, 56, was accused by the prosecution of making a "last-ditch" attempt at clearing her name by telling a number of lies under cross-examination at Teesside Crown Court.
She told the jury she threw flowers into the sea on the anniversary of her husband's "death" to comfort sons Mark, 32, and Anthony, 29, who believed he really had drowned and were unaware of their parents' insurance scam to clear their debts and start a new life in Panama.
The former doctor's receptionist said her husband wrote to her daily when they were on remand and she eventually asked him to stop.
"He used to write to me. Always, every day. His letters would be repetitive," she told David Waters QC, defending, under re-examination.
She told him to stop his letters after reading an article in a newspaper, around February this year, claiming he had been writing to another woman.
"I had requested him to stop writing to me," she told the court.
"His letters came and often I didn't open them. I didn't want to read them and I asked him to stop writing."
She is mounting the unusual defence of "marital coercion", meaning her husband forced her against her will to break the law, and that he was present when each offence was committed.
She was accused of changing the story she initially told police.
Andrew Robertson QC, prosecuting, said: "It is now to your advantage to lie about him being present because it gives you your last-ditch hope of getting away with all this. That's what it comes to, doesn't it?"
"No," she replied.
Mr Robertson: "That's what this trial is all about, you pushing everything to the wire.
"When that is proved to be a lie, change tack. When that is proved to be a lie, change tack again.
"This is the last wire, Mrs Darwin, and you are prepared to fight this case because this is your last hope of getting away with it, isn't it?
"It is nothing to do with the truth."
The mother-of-two shook her head.
She was accused of enjoying the pretence because she was good at it, and used "imaginative detail" with enthusiasm.
Mr Robertson brought up the fact she threw a floral tribute into the sea on the anniversary of her husband's disappearance.
"Flowers were thrown on the sea and that was hopefully to provide some moments of comfort to Mark and Anthony," she said.
She claimed she was dominated by her husband, and was afraid if she did not go along with his plan to fake his death in 2002, in an apparent canoeing accident outside their seafront home in Seaton Carew, Teesside, he would leave her.
When asked if she knew that lying to her sons about their father's disappearance would hurt them "in the most acute way imaginable", she replied: "I knew that. I wasn't looking forward to it."
The prosecutor continued: "But you did it, didn't you?"
She answered: "I had no choice."
The sons were in the public gallery for the third day, and heard their mother's lengthy cross-examination.
Mr Robertson asked her: "If John had said to you to, 'Anne, I want you to go and jump off a cliff', you would, because John told you to, even if you didn't want to because he had overborne your will?"
She replied: "I think that's a very unfair comparison. You were not there to see how I lived."
Mr Robertson asked the grey-haired defendant why she did not confide in her sons.
"Why didn't you, their mother, take them to one side and say, 'I cannot bear seeing you like this, the truth is that he is not dead. We are in dire financial circumstances and he's had this mad idea to try to claim some money from the insurance companies?' Why didn't you bring their pain to an end?"
Mrs Darwin replied: "Because I felt trapped."
Asked why she hugged Mark and told him "I think I have lost him" the day after Mr Darwin's fake death, she replied: "I was doing what I thought I should do."
Mr Robertson: "And doing it well."
She replied: "I was feeling their pain."
Mr Robertson: "Feeling their pain? You, their mother, could have brought it to an end like that.
"Can't you speak to your children - 'your dad has gone off the rails for goodness sake, we have to sort it out'."
She replied: "It's not as easy as that.
"We couldn't lay our problems on their shoulders."
Mr Robertson: "But you could tell them their father was dead."
Mrs Darwin said she thought the pretence would only have to last a few months before their finances would be sorted out and she could come clean to the children.
"I thought when it was explained to them they would understand," she said.
Mr Robertson said: "It's stressful carrying out a criminal fraud like this, isn't it?"
The grey-haired defendant agreed.
"But you kept your nerve didn't you?" he probed.
"No," she replied.
He asked: "You never gave anything away, did you?"
"No," she said.
She denies six counts of deception and nine counts of money laundering.
The trial was adjourned to Monday.
