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.
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.