I expected something totally different when I read 'shun back'...I thought it would be something like this:
Dear mother,
because the bible tells us 'To quit being in company with anyone called a brother that is... A greedy person or an idolater or... Etc.etc.' I can't be in company of anyone related to WT society anymore.
(and then telling every detail of the wrongdoings of WT society...) and ending with something: so you see, If I want to serve Jehovah/be a christian with a clear conscience, I have to shun you and everyone else that is JW. And I cannot let my daughter see you, because she might be affected too by everything going on in JW land.
Of course I will always love you. So whenever you are ready to see the truth and come back to Jehovah instead of following people, you are welcome."
But your letter is very clear and humble.