Eating Disorders Support Group
Eating disorders are marked by an obsessive need to control the intake and/or purging of food. This community is dedicated to those struggling on the road to recovery. Join to discuss your experience with others and find support. Get advice, ask questions, and meet others who are going through similar struggles.
The best thing you can do is to let her know over and over again that your there for her unconditionally, and how you feel about her ED. Be sure to tell her that you love her very very very very much, and will do anything to help her. Remind her of the dangers of an ED, and that you want her to be healty. Thats all i can offer for now
GOOD LUCK!
Love Kerri
That being said, despite your feelings, keep in mind that it's your fiancee's decision to challenge herself. BUT, you can always offer her resources and your listening (and really "hearing") ear. If you feel you can, let her know that you are not going to judge her, and that you would LIKE to hear what she is FEELING (since EDs aren't about looks or weight, really) so that you can begin to give her the support SHE finds helpful. Ask her what HER needs are, because everyone has very different expectations and ways of getting those needs met.
I have found that Something-Fishy is an AMAZING site, both for the ED'd individual AND the loved one. Click on "Helping Loved Ones" button to the left of your screen for resources/reading material, ways of "dealing" with the ED/what you can and cannot do, and a support forum just for loved ones.
It's not really very active, but feel free to peruse the "friends and family" group here: http://dailystrength.org/groups/support-for-friends-and-family
Lastly, take care of YOU. There's only so much you can do, and if you're not taking care of yourself, that affects things to. Find some nice "self-care" and "self-soothe" techniques, according to your tastes. This could mean: journalling, spending time with friends, going for a walk/run in nature, listening to some upbeat music, getting your hair cut (sounds silly, but it's kinda cool), learning to play/practising an instrument, etc.
Here it is: http://www.something-fishy.org
good luck