I have feelings for you
I want to tell you, but there are so many complications. For one, I doubt very highly that you consider me anything more than a friend. You are two years younger than me, which may make certain immature stupid people tease you, and I don't want you to be teased. One of your best friends has confessed to having feelings for me, and I don't want to hurt them even more than my rejection did.
I want to tell you, but I know that you would reject me, or at least I know that there is a very high chance of it happening. You don't have the same kind of feelings for me, I can see it in your eyes. I think that you already know about how I feel, and I know that you hate confrontation.
Instead of telling you, I just won't. I'll stifle these feelings, hopefully stop them, no matter how painful it is to ignore or smother them; I don't want to break our friendship apart, I don't want to lose you, I don't want you to feel pain.
Take some advice from an old fellow. Tell her!
So many stories of people who couldn't face rejection staying silent only to find years later the other person was just waiting to be asked.