"It's unacceptable," her mother said. "[Bardot is] just there to defend the dog and she does not have the right to play down my daughter's injuries. My daughter tells me every day that she looks like a monster."
The And God Created Woman star argued that, having ended the death penalty for people, France should also stop putting animals to death.
She said solitary confinement could send the dog, known as Prince, mad or make it simply give up and die.
The mayor responded to Bardot's letter by inviting her to visit Boulogne-sur-Mer to see the quality of the dog-house.
The dog's owner - identified only as Johnny - and the parents of its victim have started legal proceedings against the Society for the Protection of Animals. They say they were not told about an incident last September where the dog partially devoured the corpse of its owner, who had died of natural causes.
The dog's defenders said that was a survival instinct and, at the time, police classed him as "necrophagous by necessity".
On the SPA website, Prince was described as "a good sort, easy to get on with" but not recommended for people with families.
The SPA said it told the new owner about the previous incident, but the owner denied that.
- Independent