Hello and thank you for using Just Answer. I am sorry to hear about the troubles that your grand daughter is experiencing. It is a tough situation when your grand daughter is not treated fairly by her "dad." You should offer your observation to your daughter's attention. She needs to be the one that sticks up for her own daughter. It does put you in an awkward position if you infringe upon the family business. You are only trying to protect your grand daughter's feelings and well being. But speak privately with your daughter about the situation first. Also hopefully, the parenting classes will help your grand daughter. If your grand daughter is in fact that "bad", then she should be in counseling as well.
Hope this provides some insight. If you need more advice, just ask!!!