I agree with Darknes and I have yet to see a sent letter 'work.' I would suggest you stick to business, go into 'respond' rather than 'initiate' mode and leave her be for now.
This may not be what you want to hear, because like so many of that come here, you are looking for a way to 'fix' things. However, I would step back and let them unfold.
Work on you and rebuilding your own sense of self and your own life.
T 13 M 7 Me 48 H 46 SS 15 BD 7.14 PA D final 5.16 (H filed)
We receive & we lose, and must try to achieve gratitude & embrace with whole hearts whatever of life that remains after the losses - Dubus