I think if you just be with her and let her now that she is not alone and that you will be there no matter how long it takes to get treatment will really help her out..
I know how headstrong and stubborn people with eating disorders can be. Stick by her even if she pushes you away. I know I often try extremly hard to push people away but usually that when deep down inside I want the to hold on and not give up on me because I'm giving up on myself. Take care.

Sailaway