I'm sorry. It definitely sounds like an ED to me. Can you get her to a doctor or psychiatrist or therapist or have a family member help you out with convincing her? If she is so thin and reading calories, weighting stuff, making herself sick, that has ED written all over it.

With eating disorders, the sooner you get help, the better IMO. I got to the point where my entire identity was wrapped up in the ED. I was the girl with anorexia, and I did not want to change or think about who I'd be otherwise. I basically obsessed about food and exercise 24/7. I remember I even had this one dream where I ate an entire chocolate cake, and I woke up sweating, in an extreme panic, thinking I needed to go throw up, it seemed so real.

EDs can start affecting the heart and electrolyte balance very quickly, so she should get that checked out ASAP. One year without a period and 2 years extremely engrossed in the ED left me with lifelong osteopenia. The bone loss can be reversed a bit usually before age 30, but not much after that.