What good and bad happens when a puppy is purchased for Zoe in Chapter 6?

Because Zoe does not seem to be getting enough attention, Adam and Saskia buy her a puppy. The puppy sleeps in her room, and Zoe quits wetting the bed. Then one of the bigger dogs sits on the puppy and breaks its leg. When the vet says it will take $1,100 to fix the leg, they sell guns to get the money.