@Linkat,
A child feels threatened. A call to animal control, the dog is picked up.
When the woman has to pick up her dog a dozen times, or is confronted by animal control each time they have to come to the house, and/or fined, she'll catch on.
Seriously, no one is giving the woman any reason to change her ways. A letter?
Pfftt..
Have someone from the city pound on her door, fine her, take her dog so she has to go out of her way to get it back.
Until she feels the pinch, she obviously doesn't care.
Pinch her.