Well I would tackle it head on and ask her to stop the car so you can have a smoke, if she refuses then tell her you are going to smoke its just a case of where..... In her car or on the side of the road.

As for the food why don't you get together with the other girl and make a packed lunch ? Then you can both point out to the other person how you don't mind where she eats as you both have food in your bag .