I will try to keep this response as brief as possible, as I expect there will be a number of replies from others.
First off, allow me to say that you are a beautiful young woman, with a long, happy, healthy, and fulfilling life ahead of you. Please tell yourself this. Love yourself. Be positive - that's easily said, I know, however our mind's thoughts greatly influence our bodily health and physical well-being, so maintaining a positive outlook is very beneficial.
Second, diet is important, of course, but food should be enjoyable and delicious. Eat the food that tastes good to you, supports your body, and makes you smile. Also, I believe it's important to eat the right food for your body type. I'm a strong supporter of Ayurvedic (traditional Indian) medicine, and am myself following a diet recommended for 'Vata' type people (folks who are skinny, tend to worry, or over-think things, suffer from poor digestion/absorption etc.).
I'm currently reading a wonderful book called 'Ancient Wisdom for Modern Health', written by an Aussie chap. It's a nice, informal read that examines the wisdom of ancient civilisations, from lifestyle, to diet, to social interaction, and even exercise. Highly recommended!
Anyway, that's about it. May I wish you the very best of luck with your future! Things may look bleak now, but these experiences help to develop us as human beings. In the years ahead, you will draw-upon these valuable lessons and perhaps even help others who are witnessing similar challenges!