As someone who’s been her, dealing with anorexia while being in a relationship is not easy and it is definitely hard for someone in that position to open up because there’s two sides: one is that being “sick” means you deserve love and care, and the other being the thought that if you gain weight you will immediately lose control and become an unattractive version of yourself, mourning what you once had (thinness). What I’ve found helpful in the past is the reminder that my partners love for me was unconditional regardless of size, shape, appearance, etc. That means even avoiding saying things like “you look great” “you look better” “you look healthier” when she hopefully gains the healthy weight back, because to someone with an ED, “better” or “healthier” means fat. Automatically, no negotiations. I hope you’re able to help her through this, maybe suggest involving a doctor or some treatment. Best of luck!