You need to step back from this. That letter is from start to finish a rant and a condemnation of her. It will not reflect well on you in other people's eyes. You do not want that passed around the family table or shown to the judge. You want to take the high road and show that you have been a good person and trying to good all along, while she has misjudged you. That's all. Stay away from condemnation. It will not win you friends or influence people!
I would be happy to help you write a letter. Send the original from her to me at: purpleheiz at aol.com. I'll send you back something like what I think you might say.