I agree with Soldier. You invested money and took the time to plan this trip. That's what vacations are for: to relax and refresh you. Not to cause more misery. Spend a day with her just to show face and do some catching up, but don't let her take over your vacation time. It is yours and your husband's time together.
I understand how you feel. I have a cruise I am going on (2 days from today) with a soon to be former JW buddy of mine. She is aware of my feelings about the org and knows I do not go to the meetings, FS, etc. It was too late to back out of it since a lot of money was invested into it. The unspoken rule is that she is not to talk to me about anything JW-related and I am not to tell her the truth about the "truth". I do know that she will attempt a final plea for my return and I am already prepared on how I will tactfully handle it should it occur. Once this cruise is over with, so will our friendship. A bit upsetting, but not worth my total freedom.