It is pure bullying by her parents
Victims are now becoming the bullies.
Since the gp called the parents bullies and you countered with what I presume means that the gp is calling the victims in this situation bullies, it follows that you think the parents are somehow the victims here, if I missed something kindly point it out.
As for your question, how do you know that she hasn't been filing complaints with FB for months and getting pictures removed only for her parents to re-upload them? It would appear that the parents have made it a point of pride and believe that since they took the pics, its their right to do with em whatever they want. Since its her parents we are talking about, unfriending them on Facebook does not really guarantee that people won't intentionally (or unintentionally) find their profiles and if they're uploading these pictures as public (which I believe they are) anyone can view them. Since its an ongoing problem for the girl, I believe it would become pretty cumbersome pretty quickly to keep filling out the Facebook complaint form and getting the images removed each time they get reuploaded. In this scenario, I can't see any options besides either forcefully deleting the images and any backups that the parents might have which I think is not going to go down too well (and could result in violence) or get legal help against the ongoing harassment which would possibly forcefully stop the parents from uploading the offending pics.
Honestly, talking to you has reminded me of Juror 3 from 12 Angry Men. Hmmph lets see if I can rope my pops into re-watching the movie with me...ciao angry old man, here's to hoping you resolve whatever issues you have with your son...