What is the point of your letter? Get to it and cut out everything else -- especially all the stuff about YOUR experience. That letter is ALL about you. Sending a letter all about you to a WAS is tedious, annoying for them and confirms their own views.
Be direct, brief, and to the point. And, if you actually want her to consider it rather than merely react to you by pushing you out of her space in whatever way is most effective at the moment, then send it by email:
"I am sorry I did not treat you better in our M. I can see how my actions hurt you deeply. You deserved much better. I am sorry for pushing the D. I would like to file for legal sep instead of D, or drop either option for now. Are you open to either of those possibilities?"
