Maybe send a copy of the letter back with a note saying something like, "I'm not going to be the one to tell your grown grandchildren that their grandmother refuses to see them anymore. If you wish to inform them that your obedience to WT is more important than them stopping in to visit with you before you take the final dirt-nap, tell them yourself. And have fun telling everyone at your anniversary party that you refused to allow most of your family to come because you think if a child is sexually molested, the elders should call the WT legal department instead of the police. Of course, next year is also the anniversary of 100 years from 1914, so I suppose most of your JW friends will be too busy talking about how the latest interpretation of 'generation' could mean another 50 years before the big A."
Okay, don't actually send that, but it's what she deserves to hear for being such a WT drone.