SPAZnik, I think that she had left her child with his (never been a JW) father, who allowed her mother to take the child to the KH, not left the child with her mother. Read her post again - are your comments justified?
Most JW parents would never allow non-JW grandparents to take children to mainstream church services. Unfortunately, they can't see this from the other side. It is simpler to never allow JW grandparents unaccompanied access.