Good advice to yourself on not sending the letter. She is still to absorbed in her own self to see the difference. Let her continue to dwell in her own world, with her own thoughts. You can see this ugly person she is and you really don't want to be around that. So let her think on it, and realize eventually(however slow that trip is) that she needs to be responsible for her actions and it is not you.
Hang in there again!
Me:49 H:47 S: 16 T:27 M:25 My EA: 2001 His PA: 10/2007, 6/2013 Separated, but H still in house
Find your Shambala: a place of peace and happiness.
