As I said earlier, she wrote back with some gestures of friendship. There were still things bothering me though. I still didn't get a sense of where the room would be for my feelings if we were to move forward. The boy and I easily translated into a friendship where I felt things were reciprocated. I wasn't getting this sense from her.
So when I pressed on that issue, her reply was "I guess I didn't realize you had to bend over backwards to make room for their feelings when you break it off". What it came down to is that she really didn't like me but kept on thinking things would get better. Her way of dealing with it was to disappear and get ill rather than just be honest with me.
I thanked her for finally being honest, as that's all I wanted in the first place. I didn't feel comfortable moving forward in a situation where I had a distinct feeling that I wasn't wanted.
So in the end, I held to my standards of radical honesty and I guess I dragged her kicking and screaming into that. We're terminating the friendship. As for how the friendship will move forward with the boy, he has still told me that he would like to remain friends. It will be awkward to figure out how that'll work, though I'm willing to try.
Despite the ending and the revelation that she really didn't like my company (though it wasn't that surprising), I feel like I did the right thing in getting it all out.