My sister is suffering from an eating disorder please help?

Please help, I don't know what to do, my sister has an eating disorder, well, I think she does, she's lost so much weight and just drinks water and thinks she's fat and excersises all the time, and I know I sound naive just posting this on here as If im too dumb to research myself, but im so worried about her and I don't know where to start looking for help you see, because my parents tried getting her to talk to somebody but she wouldn't go, so is there ANY help that any of you could give me? any resources, tips, links, any ways for me to help her somehow?
I would really be so very grateful, thankyou

Okay, well seeing as I know someone who sufferd from anorexia not too long ago, I kind of know what you're going through. The thing you will need to work up to is making your sister see a therapist. But you can't tell her to do that straight away because, she probably is deniying it at this moment.
You have to encourage her to think she's NOT fat. Compliment her as often as you can, without making it obvious.
Then, you HAVE to talk to her. Don't scream, just let her do most of the talking. Warn her about the dangers. Tell her she's not fat. Listen to how she's feeling.

I have to go now but i think it's best that you speak to her, reasure her she's not alone
xxxx

How do you know she has an eating disorder. How old is she? Is she severley underweight. Force her to the doctors for a diagnosis then you can get help.
Unfortunately, if she does have an eating disorder she will become very irritable with any attempts to help. As she gets thinner she will get sick. That is where you and your parents will be able to intervene. As long as she is healthy legally there is nothing you can do... Be there for her.
She is suffering from anorexia. It is a very serious disease. I suggest you consult the doctor immedietly and get her admitted in hospital even if you have to do that forcibly. It can be very fatal if she continues like this.
hello mate,
i am a medical doctor as well as psycologist. i think your sister is suffering from either g.i. tract disorder or any compressed mental anxiety. so, therefore, (1)you have to take an advice from your family physician for final diagnosis of g.i. tract disorder, if there are no problem in diagnosis test. (2)then please consult with a psycologist. your question shows that your sister is living with all of you but nobody of your family has built good friendship about her personal affairs. you have not given your family back ground and age and profession, residential place etc. in details. by the way do no.1 then do no.2 it will solve your problem positively.