I just don't know what to do anymore. Serious question, life threatening.?

Since New Year, my best friend has lost a lot of weight. She was always thin naturally and looked healthy, but now she just looks ill and like Isabelle Caro. On one hand, I feel so pissed off with her. She acts like a complete attention seeker around everybody - talking about food with such enthusiasm - such PHONEY enthusiasm. Telling everyone how she bakes things with her new cook books and how she loves eating her cookies and cakes. When clearly she isn't eating much at all. She knows exactly what she is doing and I can't stand it. On the other hand, I remember this isn't about how I FEEL over what she is doing, and that even if she is not genuinely anorexic - she clearly has some attention seeking issues. When staying a night over her house, we took lots of pictures on her phone's camera - and knowing I would see the phone's background - she had written "eat" and a few weeks later this changed to "take laxatives, pills... ". Believe me - this is all an act for attention whereby she has even gone to the point to lose the weight required for belief. And if not I have some ****** up paranoid issues myself. I don't believe she is desperately hinting at me for help, as even though we are "best mates" she has never been one to speak on emotional levels with me, which I have always been hurt by. I am completely open to being told I am wrong here - maybe I am in denial - but I strongly disagree. Either way, there's cleaarly SOMETHING wrong - whether this is genuine anorexia or some other attention seeking problem. Help me. I don't know what to do. I feel like I'm letting her go. I'm ashamed to think such spiteful thoughts but they are what I believe. I don't know what to do anymore..