Your daughter sounds like a carbon copy of me...I too started with 'wanting flatter abs"..strange.
those of us with the AN and OCD personalities are perfectionists...I was always the "good girl" and it added lots of stress ( self-imposed ) to always be perfect. I guess you can help your daughter by stessing to her that she doesn't have to be perfect.
My healing came gradually when we moved back to the city I had originally moved away from. I gained weight simply by being on BCP's. I think I just gradually got back into my old life and the weight came back...unfortunately I carry the "weight issue" with me to this day. I am now about 25 lbs overweight (was 60 lbls over weight pre-bomb)...and it is a daily struggle.
Interestingly, I too have autoammune disorders - hypothyroidism amongst them.....
I honestly think that the AN and OCD are traits that can be controlled, but are nonetheless there for the rest of our lives.
Just keep being the great mom that you are, stay aware, and your daughter will recover. The SSRI's are essential in my case.