Hi all, I hope this is the right place to ask and I also hope I chose the right flair.

As the title says, I am contemplating sending a one-time last e-mail to someone who was a close friend and short-time romantic partner to me three years ago. I understand not everybody is the same, but I hope I can get a better perspective from you to see if it is a good idea or not. I am not confident in my own decision-making in this case. 

We did not end on good terms. While the details are not relevant and too complicated to elaborate, what it essentially comes down to is that she felt like she needed to get rid of me and she did so in the most painful way possible (to me). She apologized for everything she had said and done about half a year later, but I could not talk to her again. To this day I do not know why exactly she wanted me out of her life. It also came really sudden. I remember on a Sunday she acted normal towards me as always, then she ignored me for a week and then lashed out and did everything she could to hurt me.

We had not had contact for about two years until last November. She sent me a "life update" e-mail, which I did not understand why. She also called me the best friend that she has ever had and said she had thought about me every day ever since. I basically responded by explaining that I cannot and do not want to talk to her because she had hurt me too much, and I did not want to be reminded of that time. Admittedly I haven't been careful with my wording in that message to her. To be clear I never insulted her or called her names, but I have been quite condemning of her and it wasn't justified in that situation.

I know that I do not want or can ever talk to her again, but I do not feel well about how I left it. I would like to tell her essentially that: I won't judge her for her actions in the past because I do not understand why she did it. It doesn't mean I think her actions were okay, but knowing that she has emotional struggles I can see why it happened and that she might not have wanted it this way. (Because that is what she told me) Besides that I want to let her know that the friendship that we had was special to me and that I miss it, but ultimately it is just not possible to revive it because I cannot look at her the same way and that I hope that I can count on her understanding. 

My question to you is essentially this: Will me sending this to her more likely improve the situation (for her) or will it only cost her more energy or cause difficult emotions and is it better to just leave it, considering it has been a couple of months already?