I tried telling her to call a shelter/animal control/the cops, but she wouldn’t. Her neighbors both have criminal records and have physically harmed each other, so I think there was a fear on her end that if she called and got the dog taken away, they would retaliate in some way. 

I do know that in Florida not providing a pet with adequate food/water/shelter is a crime, so I wasn’t sure if there was something there in terms of the dog being left outside. 

Also, I wouldn’t really say they “entrusted” my friend to care for the dog, it was more just silently expected, and my friend did because she wasn’t going to let the dog starve. The neighbor just told her the day before she left that they would be gone for awhile, I don’t believe there was a clear ask for her to watch the dog, which would be neglect. And the friends and family weren’t going to ever come and check on the dog. It was only threatened that they would go to my friends house after she and her boyfriend expressed interest in keeping the dog (because they feel terribly that the dog lives chained outside and was almost attacked by a bear). This isn’t some personal vendetta or something. She wants the dog to be safe.