funny you should mention this as I was the person who did this to my normal, happy friends and family. I had never met a JW or had any contact with them before they conned me into joining them. Led on completely by a man who now I am sure only led me so I would join the stupid freaks.
At first my family was afraid and freaked out, all of my friends told me to stay away from them and my brother stopped talking to me.
Eventually my folks had no choice but to accept it but they were kind and loving and told me they would be there for me when i chose to leave them. I just laughed at them thinking they were being stupid and that i had finally found the truth that made my whole reason for being complete.
But nearly a month ago now, I finally woke up to the fact that I was in a cult. I discussed this with my folks and they are quietly happy I have left and they have their fun-loving daughter back although somewhat scarred from yet another traumatic life experience.
All I can advise is if a loved one does choose to become a dub - just let them go - most people only realise and see the truth when they are ready and wanting to, so there is nothing you can do. Just always be your same old loving self and hope that is a big enough reason for them to not leave you.