I would not bring up Bible doctrine-way to sensitive-brain will shut off. Bring a copy of the UN letter straight from the UN site. Ask if she has heard about it. Ask her what witnesses feel the UN represents. Make sure she knows you got this straight from the UN. Just plant the seed and let it go... If she is curious she will look into it on her own. Don't push too hard, you might loose her friendship.
Enjoy your trip.