First off, saying the sex meant more to you that to her is fortune telling. You have no idea if it rocked her train or not, even if her reactions at the time indicated it meant less to her. And from your description above, she seemed to enjoy it too.
About a letter or gifts in general. I learned the hard way to ask yourself (really ask) about how you would really feel if you got no response, a simple polite response, or a negative response. If you send the note with no expectations and any of the above responses would really not bother you then you have nothing to lose in sending it. But if you get no response or a negative one and you react to that, then why send anything only to beat yourself up, b/c in our situations that is the likely response. A polite response may set you up if is raises your hopes. I have learned to appreciate the clear negative response vice the polite response that I may view as a positive baby step – only to be shot down later.
In any event, IMO let her pursue you. She is the one who left. Keep her guessing about the sex and how you feel.
