My son has major feeding issues through his sensory processing disorder. My son refuses to try noodles, rice, and bread, except through all his feeding therapy he is finally eating plain, un-toasted bagles (not any other type of bread though). I hear all the time that kids won't starve themselves; however, if there is any underlying issues, like with my son's sensory issues, he actually will if he doesn't have food that he accepts. If there are any grocery stores where you are going, perhaps she can pick something out that she will eat? When I was youngster backpacking Europe, sometimes I would pick up jar baby food (apples, pudding, nothing gross) and throw it in my back pack as something to eat in a pinch as well as biscuits (cookies), etc. I was fascinated with the grocery stores in other countries and of course had to pick up chocolate bars everywhere I went. There will be something for your daughter to eat - perhaps if she has an opportunity to pick it out it will help? It may not be convential, but if she has the opportunity to pick out her own food in a safe environment it may quell some of the anxiety. Restaurants can be scary for someone with eating issues. Grocery stores will have similar foods to home. Also, I am sure there will be a McDonald's or Starbucks on every corner - something familiar.
My son has a lot of anxiety around trying new foods as well as the discomfort of many of the smells, tastes, and textures. He can smell an open jar of peanut butter from the other room and it makes him gag - his sense of smell is that strong.
I wish you all the luck. I know how difficult this is as I have been struggling with a similar issue with my own son for the past 6 years. Even after spending 1,000's of dollars on feeding therapy, it has only gotten a little better. I have gotten to the point that I can't stress about it anymore and that helps aleviate the stress off him. If he eats nachos for dinner, so be it, I follow it up with a good vitamin (that was a struggle too until we finally found the right brand for him after 2 years of trial and error).