You are either projecting or you are ops mother in law, because your stance on this is very unreasonable.
You are saying that the grandmother and outer relatives should take precedence over her own sister and parents? And that given at the moment they have a reasonably good relationship (which is questionable to say the least) then this must be prioritised over all else, and the mil’s despicable bullying should simply be ignored??
On what planet would any sibling choose to ignore such unkindness? I don’t know anyone in real life that would choose a random grandmother over their own sibling and parental bonds. It’s just not realistic or bearing any relation to real life.
DD2 should have been raised to deeply care and love her sister, and would find it unthinkable to witness such horrible bullying. It should not be beyond dd2 to talk to her grandmother if they are so close, and tell her exactly what she thinks about it.
If they are so close why on earth would her grandmother put dd2 and her son in such a difficult position? it’s power play that’s why. She cares more about scoring points over op than she does about dd2 or their relationship.
Most families work hard to foster and develop deep bonds, they do not erode away at the foundations by bullying a child.
Your total lack of empathy for dd1 shines through, the absence of decency is very illuminating. I don’t know a single person in real life that would ever behave like this towards a child, but here you are defending the indefensible. Maybe for kicks?
Op your mistake was allowing your toxic mother in law way too much unsupervised access to your younger child. She has made a black sheep of your eldest, and is being sowing poisonous seeds of division, and this will be just the beginning.
Move away, it’s not too late to influence the outcome, and change the course of the future. It’s not okay for dd2 to be brainwashed into joining a group family action designed to hurt your other child, her own sister.
I believe this has all been done to hurt and undermine the op, but why? Op’s mil has weaponised both girls to really damage ops authority and dynamic. Unless op really wakes up to this toxicity, she is set to endure much more where this came from, and it’s likely to escalate.