I would definitely write it, it is fair and important to give honest feedback, and it's not a legal procedure. It sounds like this T hurt you, I don't think you need to be concerned about criticizing her and hurting her feelings. Also, if you are no longer seeing her, she can't force amends or explanations to you and you can just steer clear. I wrote a pretty critical online review on my old T that was quite incompetent and I actually saw that another client of his had a very similar experience.