There are a couple of things I'd like to say to you, but before I do I suspect you are rather shy person when it comes to girls, as I was. This meant I, like you, would want to make contact but never did. Not while I was young anyway.
I'd think there is no way a glamorous popular person like her would give me the time of day -or worse still laugh. I still remember clearly the first girl I really liked from afar, it is one of those things.
The young lady you like has -if I understand you correctly - had more than one boyfriend in those two years. If that is the case she is probably still growing inside and finding herself. What she ends up wanting is anyone's guess.
It is very easy to think just about that one person, but I would suggest if you can you try to have more of a social life and meet others. You never know what will happen. I found somebody (after a couple of crushes I must admit) or they found me, not sure
It worked out despite my shyness.
I guess when you are given such a horrible message by your doctor it does make you fearful of the future and angry. Despite what you might think now I'm not sure that the anger would necessarily be a put-off.
I had a friend for many years who's body would go into rigid spasms once in a while, leaving him frustrated and angry. The thing was though he was angry at himself for not being able to do what he'd planned. He was in pain and stuck.
That anger was never turned on anyone else, so when I was right there and saw it happening and his mood react I simply felt sympathy, and frustration of my own I could not help. No way it stopped the friendship.
I think Sophie_M's suggestions, particularly the Kids Help Line are pretty good ones