Sometimes, the SH*T just has to hit the fan. Seems like it is time for it to happen. It just burns me up, how the JW's can behave the way they do, so unkind, but then expect that they are "entitled" to something. The grandmother made her bed, and she should sleep in it.
I would not be very happy, if I left my children in someones care, had expressed my wishes about something so serious, and then found out that the caretakers went against my wishes.
You really do need to express your feelings, and let your wife know in no uncertain terms, she has no business taking the child to the grandmothers. Ask your wife if she wants to lose her sisters trust, because that is what will happen.
Perhaps if the grandmother actually suffers the consequences of her own cruel actions, maybe she would learn a lesson, that she has to change her behavior if she wants to see her own grandkid.
Yes, I take this personally, if that's what it sounds like. As it has happened in my own family. My parents made the statement about my disfellowhipped sisters son when he was a baby "I'm not going to bond with him, since he is going to die at Armegeddon". Like I just reminded my father, my sisters son is now 11 years old, and they have aboloutely no relationship with him.
btw, they piss and moan an complain that the boys worldy grandma has such a close relationship with him.