Sadie Hartley, 60, was stunned with a cattle prod and stabbed at her home in Helmshore, Lancashire, in January.
Preston Crown Court heard Sarah Williams, 35, exchanged naked photographs with Ms Hartley's partner Ian Johnston in the weeks prior to the death.
Ms Williams denies murder.
The court has heard Ms Williams was obsessed by Mr Johnston, 57, and "eliminated" Ms Hartley with the help of Katrina Walsh, 56,  who also denies murder, when he refused to leave her.
Mr Johnston, who had been in an "intermittent", "intimate" relationship with communications director Ms Hartley, began a sexual relationship with Ms Williams after they met in December 2012.
The former firefighter told Ms Williams the relationship was over months later, he said, but she kept contacting him in person or by text and even sent an anonymous letter to Ms Hartley, boasting the sender had had "fantastic" sex with Mr Johnston.
John McDermott, prosecuting, said Mr Johnston and Ms Williams exchanged naked photographs on 3, 4 and 5 December last year.
Mr Johnston said he didn't block the messages and responded "in kind" to Ms Williams' messages.
But he told the prosecutor he did not seek to rekindle the relationship and was "distraught" when he read the texts the next day.
There were further similar exchanges between the pair on Christmas Day, and again 10 days before the murder, Mr McDermott told the court.
Mr Johnston had been in Switzerland when the messages in January were sent, the court heard.
Mr McDermott asked: "What were your intentions with Sarah Williams once you would return to this country?"
Mr Johnston said: "Nothing at all. I can't recall half the text messages."
Ms Williams and riding instructor Katrina Walsh, 56, of Hare Lane, Chester, both deny murder.
Walsh is said to have played a key role in helping her friend to "eliminate" her love rival.
The trial continues.

Shares in Chevron fell 1.1% and Exxon Mobil dropped 0.7% as oil prices fell almost 4% on worries that producers will fail to agree production limits.
Brent crude fell $1.74 to $46.50 a barrel, while US crude was down $1.79 to $45.29 a barrel.
The Dow Jones fell 23.7 points to 19,121.60, while the broader S&P 500 index was barely changed at 2,201.72.
The tech-focused Nasdaq index rose 11.11 points to 5,379.92.
Earlier, official figures had indicated that the US economy grew faster than previously estimated in the third quarter of the year.
The economy grew at an annualised rate of 3.2%, the Commerce Department said, compared with an initial estimate of 2.9%.

Stargazers and photographers around the world have captured some stunning images of the spectacle in recent days.
Here is a selection of their images:
The Northern Lights are caused by the interaction of the solar wind - a stream of charged particles escaping the Sun - and our planet's magnetic field and atmosphere. Find out more about the Northern Lights.
The lights themselves are often visible in Scandinavian countries, but also in northern parts of the US and Canada.
The Northern Lights were also seen off the coast of Norfolk, England too. Thanks to Ben Gadsby-Williams for this time-lapse video.
Thank you for sharing your pictures with us.
You can email your pictures and video to yourpics@bbc.co.uk or upload them here.
Compiled by Rozina Sini
The partner of a woman killed with "demonic savagery" exchanged explicit texts and photos with the woman accused of her murder, a court has heard.
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US stock markets closed little changed, but energy shares fell as the oil price slid ahead of Wednesday's Opec meeting.
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The Aurora Borealis also know as the Northern Lights have been making an appearance across parts of the UK.