Calling child protective services questions?

i have a friend and she is terribly anorexic. she is 5 feet tall and weighs under 60 pounds. she has been like this for months and her parents aren't doing sh*t about it. my dad, who is a physician, is concerned she will die if no one does anything. she does not eat anything except for crackers for dinner, and excerices excessivley even though her doctors and nutritionist have told her no exercising AT ALL. she continues to ignore these requests claiming she is fat and she can't eat as much as she should and not exercise. her mother is also an anorexic, and she has severe mental problems. the father is withdrawn, (he has a distorted view of reality and is barely home due to his wife's mental condition) thus, my friend has no backbone or support, and through many attempts my friends and i (who are also her friends) have no where to turn. i can't watch her waste away like this and know that her parents are doing anything to help her at all. they are just watching her die also. i would like to call CPS and alert them but i do not know what to say, how to say it, and am i old enough? (15 years old) many other parents have wanted to call, but are scared of the outcome. and is child protective services the right place to call? or is there a better place?