I don't think they intend to hurt SD, but they do this again & again. They did it to us, for years by putting mum before their own son. It was crazy, sick & absolutely destroying & drove him to a breakdown & put me in counselling! She has always had some kind of hold over them, & we kind of understood it when SD was living with her mother (she would use emotional blackmail to get money out of them) so there has always been codependence. But, when SD left her mother
3 years ago we thought things may change, but they didn't & now not only are they continuing to hurt us, they're hurting their granddaughter too.
We cannot have any more to do with them because to do so would be dangerous. It's a shame, it really is, but we have no choice because they really won't ever change.