Warren had been in a 14-year relationship with another of Martin’s daughters, Clare, who had died suddenly in 2021, aged 29.
Esther Martin was described by her daughters as having had an “infectious laugh” and grand sense of humour.
They said she had just been “regaining her life” after Clare’s death.
“It was the first time in a long time she was starting to feel positive,” Martin-Coppen said. “Warren’s actions by not being a responsible dog owner directly impacted that day.”
Warren, now of Addlestone in Surrey, was the first person to be prosecuted under XL bully ban.
He will be sentenced on 1 April.