Welcome!!
I would suggest that you edit.
What really matters to you? What are you most passionate about? Stick to the essentials.
I would leave out the excruciating details-or better yet, if it will be emailed, give links to news reports. Give brief quotes and the reference info so that she can look it up if interested.
Make sure any info you give is pertinent as regards YOUR reasons. Pedophilia, the WT indifference to people who need protection, the dishonesty of their biblical arguments, out of context 'support' for their teachings. Whatever matters will stand out more in a brief letter than in a treatise. They are NOT preaching the good news of the Bible-that is what gets to me, so that is what I would focus on, because it matters to me. Other things do also, but we all have the things which touch us the most. On other approach might be to focus on the things you know would touch HER the most that you can give solid information about.