The most effective method of attacking someone is to be civil about it. Don't use curse words, don't use all capital letters or more than one exclamation point at a time, use proper punctuation, grammar, spelling, and capitalization, and be mature about it. I would end the letter with, "Sincerely," because it will bother her more that you're attacking her, but not making a total ape out of yourself like she wants to in response to you.