She sounds exactly just like me. Very picky, couldn't handle foods touching, if something hung off the fork the wrong way I couldn't touch it... (I'm still like that to a degree) I only ate a few bites of food a day. I had problems with textures, sauces, liked my hamburgers dry and no sauce of any kind on pastas... I drank milk and ate wheat bread slices and that was about it. I was often so weak from hunger that Iiteraly couldn't eat, or it would make me feel sick if I ate, I never really realized that was due to not eating in the first place. I was very tiny, rail thin, never on the growth charts. Even as an infant, I would only eat maybe one or two baby spoonfuls of food a meal, sometimes the whole day. My mother tried everything too with me.
I didn't have an eating disorder, but by the age of 11, my parents got fed up and took me to an endocrinologist. I had the bone scan of an 8 year old.
The Dr. told me if I didn't start eating I would not get any bigger and that I would have to be hospitalized and fed through an iv... and they were serious too. That pretty much terrified me and I began eating, slowly but surely. The Dr 'prescribed' my parents give me the Carnation shakes and bars, more healthy fatty foods to at least help, encouraged me to snack throughout the day on things (like a deviled egg, handful of peanuts) no milk before meals b/c that would just fill me up so I wouldn't eat, and to help get me involved in meal planning and food preparation, so that helped a little. Once I started eating, my bone scan increased in years in a rather short period of time.
Now, I am just under 5'... right where my Dr predicted I would be. Even to this day, I have to remind myself to eat, having kids who get hungry helps, so I eat when I feed them, but if I didn't have kids I would still have a difficult time, because I usually work right through that hunger until I get weak again and crash.
Also, you have to worry about her developing hypoglycemia, which could turn into diabetes, or at least those symptoms of weakness, dizziness from blood sugar crashing.
Anyways, let her know about the iv and the potential damage to her health she is doing and take baby steps with her.