Onlineguy,
Well my first impression upon reading your post, I would think you over reacted. I say this because Ive dealt with an emotional ex recently, and the way you just explained things reminds me so much of how he would blow things out of proportion.
There were very valid times that I just could not respond to him, such as when I was at work and busy or when I was trying to get something done.
For granted you were asking a simple question and it would have been nice to get a response and not feel ignored, but it sounds as if you expect to be ignored therefore the minute she doesn't say something in return right away, you assume the worst.
I could very well be wrong, and just stuck with the memories of my own recent, and unsuccessful, attempt at being friends with my ex. Things were fine until he finally found the leverage to turn things against me. I figured out that was the only reason he was even still talking to me. He couldn't stand that he was the one at fault... which we broke up for the same reason you and your ex did... he was too needy, too insecure, and untrusting.
With all that said, I think its best for you to just continue walking away. It seems as though its just tearing you up trying to be friends with her. I don't think its fair to you or her at this point.
She will probably be a little hurt that this is how you are going to end things, but she may have expected this to be your behavior anyhow. I know I definitely expected my ex to behave like he did... I tried to avoid it, but in the end I just let go and let him be, I let him turn things against me cause then he was able to move on. It sucks he hates me now... but I feel OK with that sine I don't feel like I have to play nice or try to always reason with him...
Ok well I hope this made some sort sense. Just try and let things go... You will be better off.