A friend of mine was morbidly obese, and opted for gastric bypass surgery. She nearly died several times, had horrible complications, looked gray all the time, had heavy periods like you wouldn't believe, and one day I asked her why she has decided to do this, considering all the difficulties she'd had.
Her response? My husband didn't allow me to handle anything he deemed important. All I could do was go to work and come home, and take care of the baby. THE ONLY THING I COULD CONTROL WAS MY EATING, SO I ATE. AND ATE. AND ATE.
That statement, from a 45 year old woman, is what I think of when I think of your daughter. It's the only thing she can control, and with the food issues, she can control you, too, and by extension, the entire family. That's a heck of a lot of power she has, just by taking (or not) several bites of food. I'm not saying there aren't other issues by any means, but I wonder (as I often have with Miss KT over numerous things) how much is "can't" and how much is "won't."
Hugs. Hope you can get some peaceful solo quiet time soon.