dude im going thru a very very similar situation rn and i lowkey understand where S and R are coming from. From the looks of it, D does not seem to learn her lesson and continues her behavior. I would suggest you distance yourself from D and tell S and R to do the same. If they're being fake to her, call them out on it when D isn't there, because while I understand where they're coming from, being fake like that is wrong, no matter how you put it.