Do I worry for my friend?

Well I was talking to my friend the other day and she seemed really stressed out, so I was just talking to her. First of all, she is very skinny to start off with, she is underweight. And she said that lately she has become obsessed with her weight. She says that she is now constantly thinking about her weight, like that it preoccupies her mind, and she can’t make it stop. She says that she is really fat and she is like crawling in her skin. She says that when she eats all she feels is the disgusting greedy fat feeling, even when she eats something little. She says that she hates eating out all of a sudden because she feels like everyone is watching her thinking how much does she want to eat, she is so fat. She can’t stop picking out all of her “flaws” that I can’t even see. Like she says now she sees things that she never saw before. Every time she puts something into her mouth she must go have a look in the mirror and see if she has gotten fatter. I think she is loosing it. Like she hates wearing tight clothes any more and like she thinks everything shows off her fat. But I can’t see it. She told me she doesn’t like hanging out with friends any more, she likes to be alone. And then she told me that she always makes herself throw up but then right before she does she stops. She hasn’t yet stopped eating junk food and stuff, but I believe she slowly will cut out all foods by the way she was talking to me. I feel like she has the mind of an anorexic but she doesn’t eat like one. But I am scared that she soon will.

Should I be worried for my friend? Does it seem like there is something wrong here?? Please tell me what to do.

Thanks.