Im scared that my friend might have an eating disorder...?

Okay so school ended last week, and the last week of school we got to sit where ever we wanted in the cafateria. So i got to sit with all of my friends and one of them would get a school lunch...but she wouldnt eat any of it, i thought maybe she wasnt hungry that day, but it happened again and again. Im not sure how long its been going on, but its kind of scary. I metioned it to another friend and she said she'd keep an "eye" on her but that is kinda hard over the summer. I just hope she doesnt come back to school next year dangerously thin.

Maybe you ought to let her parents know about it. some ware down the line, some one suggested she was fat, and she listened. her health might be on the line now. A friend will seek out help and modivation to get her better. And if the parents have to be told, she will blast you for telling, but at least, she will live

Do you know her parents or are your parents friends with her parents. You should probably tell an adult and have them handle it.
It's nice that you are worried, but what is your question?

Can you not spend time with that friend over the Summer? Perhaps she's just a meal skipper, and doesn't have an actual eating disorder.
Is it a close friend? I would assume not if you aren't going to see her until next year. If you are really concerned you may want to talk to her family and ask or you may want to ask if there is anything going on in her life that is upsetting her. Eating disorders are about controlling the world around them. People who have them feel like they can only control their bodies and what happens to it.

Ultimaly it depends on the relationship you have with the girl.