Crossroads, well done for not letting them have power over you.
we all lose it with our family members from time to time, how ridiculous it would be if every time we do we had to explain our actions to some external body. You and your family's issues are nobody else's business. It's tragic that they are prepared to lose their daughter over a different in faith, but it's just sad evidence of their complete indoctrination.
It's just mind boggling that the witnesses have fought in the courts for freedom of religion, yet when one of their own exercises that right, they seek to destroy their life. Imagine if when they went on the doors to convert people, all of those converts were shunned completely by their non jw family. Personally I converted from CofE, my parents were disappointed because they thought (rightly) that jws were a cult, but they continued to support me and my jw husband emotionally for over 20 years. My husband converted from Catholicism, again his family were confused, disappointed, but they continue to love, support and communicate with him to this day. How many jws are grateful that other religions don't enforce such harsh shunning practices. Evidence alone this is not the true religion identified by love.
i am so sad for you facing the loss of your family. I would write them one sign off and then leave the ball in their court, something like:
I love you deeply and I want you to know I will always be here for you whenever you need me, and I a will always want a loving relationship with you, we have big issues to face in our future, the possibility of grandchildren, or inevitable old age and sickness, things which should bring a family together. I have changed my beliefs, I am sorry that is hard for you to understand, but I haven't changed my love for my family. I hope that you can respect we have different views from now on and 'agree to disagree', I won't critisise your faith and am sorry if I have done so, if you don't criticize my beliefs and decisions either. But we can continue to support eachother. If you feel you must shun me and my husband I am sorry and heartbroken for that, if you do so because of what the writers of the WT have told you to do, please remember that they will not suffer in anyway for giving that counsel, but you will and I will suffer greatly if you follow it and sever our family relationship. The choice is yours.