I think my friend is anorexic?!?

Okay she's sooo skinny. Plus she tells me that she's always tired, sometimes gets depressed, and once fainted and she always feels cold. I looked online and it said that those were some symptoms of anorexia nervosa! I barely even see her eat and once I heard her mutter something about "hating to eat"... I'm so worried and scared... What should I do?