The dog will likely be put down after the 30 days observation for rabies. This is the direct fault of your sibling.
Your sibling is 100% responsible for the fence. If it is not sufficient to hold that dog, then all your sibling had to do was not have a dog OR make arrangements with the landlord to pay for the fence to be upgraded.
There is zero 'right' to own an animal if you are unable to provide adequate care and training. I hope your sibling does get sued and, if the landlord were smart, they may not be able to renew their lease. I hope both of them get never healing boils all over their body for using a shock collar on an already struggling animal. Sorry, not sorry, but they can both rot.
The losers in this situation are the dog, the little girl, and the landlord who is sharing liability for that dog escaping the fence line.