This happened to one of my closest friends that I grew up with. She rang her parents to let them know last year that her boyfriend of 4 years had proposed and they were planning to get married the following year. She had been disfellowshipped at 20y/o and her family had kept in reasonable contact with her since then. Her father was extatic for her and congratulated her, her mother (a very humble jw woman) was of course not so pleased. During the week that followed the elders came to speak with the mother as they had heard of the news, to tell her that she was not permitted to attend her daughters wedding, as if she did she would likey face a judicial committee...the strange thing is they can never tell you for certain either way, until you've actually done the "wrong" thing....anyways, the mother rang the daughter 1 week later to tell her that she would not be able to attend the wedding. The mother hadn't even spoken to her witness husband about it before making the call. The father told the daughter that nothing would keep him away from his daughters wedding. The crazy thing is that her father has always been a little rebellious and seems to get away with these things they just say "that's Ron for ya". That cold hearted phonecall really broke my friends heart, and she has decided to put off the wedding until a future time.
I suggest your sister tells your father exactly how she feels about this situation, tell him to stop acting like a scared child, and be a real father to her. If he can't be a real father for her, and be happy for her, then that's on his conscience. Tell him to stop blaming the elders for putting him in such a compromising permission, and take responsibility for himself. He chooses to be a jw afterall. grrrrrrrr, it makes me so mad. Bloody adults behaving like lost children, so mad!!!!!!!!!!!!!!!
My sister was disfellowshipped at the time of my eldest sisters wedding, she never stopped attending meetings, and returned within 8months...however at the time of the wedding she was allowed to attend the ceremony at the KH only, we were told to lie to all our extended family members and tell them that she turned terribly sick between the ceremony and the reception and therefore couldn't attend!! I want to vommit when I think of that now. The witnesses know that this shunning at such a special occassion isn't acceptable, and they know that reasonable loving people who aren't JW's would never comprehend how they could behave in such a way, so therefore they have to hide it from him. I suggest your sister exposes the truth about the "truth" to all her non-witness family and friends, afterall she had nothing to hide, it is her fathers faith that keeps him from attending her very important day (I'm assuming that your sisters is no longer as heavily involved??).
All the best to her, she needs your support, she'll never forget that you were there for her. Let us know how it all goes:-)