It seems that some (not wishing to at all imply all dads) dads, after a divorce, can use the excuse "well her mother brainwashed her" when their child doesn't fit the mold he has for her. We aren't JWs, however my girls are going through a twisted version of this too.
The oldest, who has been living with him the last year and a half (long story as to why...) needs to stay until June to graduate from high school but he wants her out now because he has a new girlfriend living with them and her daughter is prettier, better student and mostly doesn't ever talk back (she's told my daughter she's scared of her mother and from what I hear, for good reason). My daughter stands up to him. Now he wants her out now, but I live 5 states away so he needs to keep her until June. The drama is unbelievable.
The younger daughter lives here, and he was so abusive to her last summer (he's a drunken ass) that she had a break down when she got home. She wants nothing to do with HIM and hasn't been back. For him, he tells everyone all is well and that she's been "too busy" with her school, theater group and work to visit. Yet he knows differently and doesn't even call her to chat.
I, of course, have brainwashed the girls to have no respect for adults and the size of his wallet.
I hope your granddaughter understands this is no failing of her own. On one level, she probably gets that, but there's a little girl in her that is still very likely hurt. They all want a good "daddy," too bad they don't all get one.
For ANY reason, rejecting your own child for being different from you is just wrong!