Nice letter - very warm and positive! Is there something special about having waited one month and now replying? Why not 2 or 3 months? Didn't she say she did not want to communicate with you but you put in parenthesis (at this time) - is that what she said: "at this time"? No where in your reply do you acknoweldge what she said. Is there a reason for this? E.g., "I appreciated hearing from you and realize you said you did not want to communicate with me at this stage but I just wanted you to know that I've been thinking about you and the good times we shared....etc."
My apologies if you've already considered this but here goes: Realize that in sending the letter you may feel hurt in some way should she ignore your letter and/or not reply.When we reach out to others, it is normal to hope they will reciprocate and/or gain some sense that we are not evil, horrible people - and when nothing comes back, we could feel empty or letdown.
All the best.