Abused or abandoned is a very extreme example though to be fair.
Yes, I am sure that they do not hurt Prinny on purpose. She is not underfed, she has a clean dry place to sleep. They exercise her, all of these things are good. And like you say she is always with the kids in the evenings, so she included in the family in that way, which is lovely. I am not claiming that they 'abuse' Prinny or anything horrible like that.
However, I personally find it unacceptable to leave your dog completely on her own in a brand new environment (for hours!), it will cause her anxiety and confusion - this should simply not be an option to them. One of the adults should have stayed with her, it's just completely thoughtless toward her.