I would also very much agree with nvrgnbk that it's timing. My sister is showing signs of doubt now so I am very slowly dropping little tidbits of info to her. A year ago I would have never even thought about it.
That is what worked for me. But it was mostly seeing others that had left and that they were happy and productive. My dad was the first one. When you are living in the same house it's hard to miss it. He never once said anything to me negative about the JW's. His hapiness said it all.