Help for a friend with an eating disorder!!!?

My best friend has an eating disorder and I don't know how I can help her! When we hang out on the weekends all she dose is binge eat until she makes herself feel sick. She has never made herself throw before but after she binges she always complains about all the food she just ate and how fat she feels. After the binging she will go on a 1 to 3 week crash diet where she only drinks water or juice and will have nothing to eat at all. I鈥檓 really worried because the crash dieting gives her bad headaches and she gets really dizzy and tired all the time. I don鈥檛 see any point in her dieting because she hasn鈥檛 lost any weight since she started and this has been going on for over a year now. I have talked to her about her problem but she always makes up an excuse for her eating habits. I find that she is either lying to me about the amount of food that she just ate or telling me that she ate when she really didn't. If anyone has any tips to help me deal with this that would be great.

take her to a psychologist for real.

She is telling th truth about over eating. She is lying about dieting. And she is totally missing the part about exercize!!!
Go to an adult. Normally I don't suggest going over their heads, but it seems like you've already tried talking to her about it. Eating disorders of ANY kind are dangerous to one's health. She'll be mad for a bit, but she should turn around and realize you are saving her life. She needs treatment. By not doing anything, it's almost encouraging the behavior or being a "silent approver". Even if you don't approve, to those with an ED it seems like you're letting them do it and get away with it. ED's aren't just about weight, there is 99.9% of the time some underlying cause.
Lots of experience with EDs
sounds that your friend is at the part of her disorder where she really needs helpl, when you have anorexia you will just starve all the time but once you start binging your body is saying "give me food" but to compinsate for the food she restricts find the book "Life Without Ed" at amazon.com or lifewithouted.com this book is AWESOME and will really help your friend and talk to her parents and see if maybe she can see a therapist if she does this much longer she could hurt her body and even be fatal hope I helped.
experience for many years with ED (eating disorder)