oh @Raspberrysins I feel your pain, it is so sad to see the changes the ED has made to our children's bodies. Take heart in knowing that as she gets well that will change, though in my experience DD may not like the change! always a new challenge on this journey
Re the time choosing a sandwich, the advice is to take choice away from the young person, as the ED voice will be telling them every choice is a wrong choice. Carers need to present food as a decision made, calmly stating it's the right thing for them.
I know that's easier at home, we went away a month into dealing with this and there were times DD was involved in choices then as I couldn't think of another way, but you should limit that if you can. I found a brief advance discussion helped, preparing for any choices and ultimately making that choice myself if it wasn't resolved quickly. We also went separate ways as a family if needs be, DH and DS went for what we would normally do when away, DD and I went elsewhere to avoid an 'audience' and, in some cases, back to our room to eat familiar agreed food from home to keep the intake up and reduce the pressure when we were out and about.
I also get that the book and forums can be scary, try see it as forewarned is forearmed. Not all young people experience everything you will see here, and lots make at least a partial recovery quickly. I found knowing how this could go gave me strength to persevere with those early difficult meals, and to take comfort in every tiny positive step.