Hi there and thanks for your question.
Impetigo is as you probably know, a bacterial infection involving a particular type of Staph bacteria. While it is not common for a person to get this from their dog, it certainly is possible.
If your dog has any lesions such as pustules or sores (i.e. the sore on her neck!), then your vet can perform a bacterial culture to determine if the dog is carrying this type of Staph. However, some pets can carry the bacteria on their skin and not have any clinical signs. A culture of the skin can be attempted, but it is difficult to get results without lesions.
Another possibility is that a bite or scratch from a cat or dog can cause a wound which could drive Staph bacteria that was already present on the human's skin deeper into the wound. The Staph may not directly come from the dog, but could have resulted from the inflicted wound.
I hope this information helps! I will be online for a short while more. So, if you have more concerns about this question you can just hit reply. However, my baby will be waking up from her nap soon and I will be offline after that. If that happens I will respond when I come online again. Or, if my answer has been sufficient, please hit accept. Thanks!
The above is given for information only. Although I am a licensed veterinarian, I cannot legally prescribe medicines or diagnose your pet's condition without performing a physical exam. If you have concerns about your pet I would highly advise contacting your regular veterinarian.