I have made the grammatical corrections as you requested:
"It was a surprise to see you the other night at XXXX room. I am glad it happened because strangely enough, it helped bring closure for me just like my divorce did. Both experiences brought pain and left my heart in a state of vulnerability. It is only in this state of total vulnerability that I gain clarity to reconnect with myself and start my new journey toward wholeness. I am able to accept and surrender to my current situation and learn to love different aspects of myself and others - the good and the bad. In looking back, whatever happened between us happened for a reason. The way it turned out served as a catalyst to accelerate my personal transformation and I am a better person because of this. Since I saw you last Friday, I have put the past behind me and am ready to move on. One thing unexpected coming out of this is I have discovered Argentine Tango and love it dearly. In coming months, I plan to take various dance lessons and attend different dance events. We may run into each other from time to time and I'd like to be able to say hello to you. Andreas"
I would like to make a few suggestions, however. It may be too soon to expect that either of you will be able to make casual conversation. As you noted, it has only been a few days since the breakup. It may seem a little cold to her to say that you have already moved on and had a personal transformation in such a short time, even though your intent is to let her know that you are okay with the breakup.
You might consider just taking out that one line about personal transformation and leaving the rest of the letter as it is.
No matter how well written your letter is, I fear it is too soon to expect her to be able to have a casual friendship with you. There is always some discomfort after a breakup. You might want to wait a month or so before sending this note.
Enjoy your new-found interest in the Tango!