OK, I hear what you’re saying. I was trying to think of a way to do three things:
1) Agree on a common objective to set the path for you two to take, knowing that she will try to jump off later. Could either of you say what this common objective is right now? 2) Get her in touch with her feelings and what she really wants (which is to be loved, not to have a buddy). I see this as a requirement for point 1, but it may take a longtime to do this. 3) Get you two on the same team be appealing to her needs.
I suppose the other route, which I had to take, is to be more confrontational and tenacious, and in so doing prove to her how much you care. I just think there will be lots of times when you will have to do this.
I also think your letter is just pushing on an issue she is trying to shut down. I don’t see it making much difference whether you get sex or not. I doubt you do. So without a counterbalancing feeling in her that you are on her team, I’m not quite sure what bringing up the sex issue will accomplish. I do think you need to keep that issue alive, but maybe for the bigger war, not this initial skirmish?