To Thundercloud .......
I think writing the letter is a very good idea - even if you don't send it to her.
In the Fall of 2013, I wrote my oldest daughter a letter while copying my youngest daughter. It was to tell her how I felt .... how I didn't like how we seemed to have grown apart .... and that I would like to talk to her about it.
She replied but soon backed off meeting with me to discuss anything. BUT - my youngest daughter read it - then e-mailed me a long letter. It impacted my youngest daughter so much that ever since that letter ... she has called me once a week - just to talk.
We talk about serious stuff, nonsense and everything in between. My youngest daughter told me that she realized that both of her parents are getting older ... that there are health issues ... and that we won't be around forever.
The youngest did move - with a substantial job promotion - about 4-months ago, but i get a call from her every Sunday night. We have gotten closer .... and it was thanks to a letter written to my oldest.
And even if you do tear up the letter - and not send it out, it will have done you some good just to write it ... and to re-read it!