That is very good of you to care for your friend, she is very lucky to have a friend like you.
Em does she mind talking about it? The other person who replyed is right, she is not going to stop feeling the way she does because you are worried but if you explain to her that you care about her and that what she is doing to herself is harming her and she deserves better.
Eating disorders are so complex and a few years I probably would of said just be there for her if she needs you but now I think I will say different. I know how much eating disorders can destroy your life as I have seen it more times then I care to think of and I have lost a very dear friend to it.
It might not be very serious at the moment but once she startes getting sick and eating differently then that is a sign that something has been wrong for awhile now and its just manafesting itself now.
Your friend would need to go to a doctor just to get blood tests to see how she is doing medically. I would really advice her to see a therapist or something like that because this will not go away on its on although she might say it will, it won't. An eating disorder is so complex that even the person going through it won't fully understand why until they are recovered.
People who don't eat or make themselves sick do so because they don't know how else to cope with life. That is their way, the same way some people use drink, drugs, we use food.
You can only be there for your friend and support her decisions but do say that you are concerned about her and you would like her to get help.
She will do what she needs to do but give her time.
Also I just want to point out something. I have an eating disorder and I became very intravert, where I didn't really want to go out with friends anymore and I just stayed at home as a result I lost alot of friends. They did not realise what I was going through and they thought I didn't like them but that wasn't the case at all, I just wasn't sure how to talk to them anymore.
So if your friend does back off a little don't be worried because that is very normal and it doesn't mean she doesn't want to be friends with you anymore, it just means that she is going through alot of things in her head and she kind of forgets how to chat and have fun. So be there for her as much as you can but also remember to look after yourself because having a friend with an eating disorder can be tough.
I hope that helps a little bit! Your a very good friend to her, all the best!
Xxxx