The alleged motive for Sarah Williams murdering love rival Sadie Hartley "does not stand up to close scrutiny", a jury has heard.
It is said that Williams, 35, assassinated Ms Hartley, 60, so she could have the businesswoman's partner, Ian Johnston, 57, to herself.
But in his closing speech at Preston Crown Court, her barrister, Gordon Cole QC, said it made no sense for her to cut off the "financial lifeline" provided by her long-time lover, David Hardwick.
Williams first became a couple with married father Mr Hardwick when she was 17 and he was 57, the court has heard.
Labelled in court as a "sugar daddy", the semi-retired businessman David Hardwick, 75, paid for a string of holidays - up to 12 a year - for himself and Williams, with more already booked when she was arrested.
He also gave her £75,000 towards buying a house and transferred £320 per week into her bank account.
Mr Cole said: "There was a price to pay by Sarah Williams if she was going to set up home or have a permanent relationship with Ian Johnston. The price was the cutting off of her financial lifeline from David Hardwick, is that she wanted?
"You may think, bearing in mind how long she has been in that relationship with David Hardwick, that this was not about cutting off that lifeline, this was about having a relationship that David Hardwick did not know about.
"She had done it in the past and she was going to do it again.
"The idea of having to get rid of Sadie Hartley, we say when you analyse all the evidence relating to that, is not the picture that comes out.
"We say the question of motive does not stand up to close scrutiny."
Mr Cole said that unlike her co-defendant, Katrina Walsh, 56, - accused of helping to plot the murder - the ski travel firm sales advisor had gone into the witness box and given her account.
Addressing the jury, he said: "It is your decision as to whether you think she is lying or not, whether you are sure she is lying.
"We accept that this was a horrific murder, no doubt about that. We are all aware and are not immune to the feelings of Sadie Hartley's family, their grief and the horrific events they have gone through but so far as Sarah Williams is concerned she says she did not kill Sadie Hartley, that is what she says."
When giving evidence, Williams said she did not know who the killer was but said the evidence could point to horse-riding instructor Walsh as the perpetrator.
Mr Cole said that Walsh had "prejudiced" the case of his client by not allowing them to address "unanswered questions" such as whether somebody else was involved in the murder - an "unknown accomplice".
He added that there were "real gaps" in the totality of the evidence and that jurors should return the verdict that Williams was not guilty of murder.
The Crown say Williams drove to Sunny Bank Road, Helmshore, Lancashire, on the evening of January 14 and incapacitated Ms Hartley with a 500,000-volt stun gun as she opened her front door, and then stabbed her to death.
Williams, of Treborth Road, Blacon, Chester, and Walsh, of Hare Lane, Chester, deny murder.