Feelings change all the time. You can't help how you feel and if she doesn't feel it anymore, she doesn't feel it anymore. You would think anybody would be happy to have what you provide and it's very perplexing when it just isn't enough. It doesn't sound like she was prepared for this when it first began and was still trying to cope with it throughout the whole relationship. This wasn't just out of the blue was it? You could you see the signs pointing up to this before Spring Break when you look back on it right?
Especially at this point of our lives when we are growing up very fast and changing constantly, it's very common to be scared of commitment this early on. I don't want to say she's insensitive too, but you having a debilitating disease could be hurting any future plans she may see with you as well. I can imagine the pain you are going through and your love for her isn't just going to go away. The guilt she is going through has to be very difficult so I don't know if the book of you two is completely over yet. However, this is what she is wanted and all you can do is let her have what she wants, and the consequences it comes with.
I don't think the love you have is very common at your age and the way you could show it is very different. Take pride in the fact that you have this powerful a feeling for somebody and are able to offer what many men won't or even can't provide. I can sadly admit that I have never felt the way you have felt about this girl and I have a few years and a few more relationships on you. Maybe she will realize what she missed, and maybe she won't. There isn't really much you can do or say. I'm sorry.
Just keep all the pain and anguish and things you want to say and the things you feel away from her. Vent them anyway possible but to her. You won't accomplish anything if you make her feel guilt or pain you are feeling.
Waking up next to a beautiful girl,
Step outside and say hello to my beautiful world.