I also think you should send it to Miichan~ It has thoughts of many international fans, and there being a lot of international fans for her, I also don't want her to feel like fans outside of Japan are now unsupportive of her.
A suggestion I have... Perhaps if possible, Miichan has a G+ right? You could try to send it to her there, although I'm unsure if she will even see it or if she even has one anymore. Another way is... I guess if you know miroku48 on Tumblr, I think it's a far stretch but if you could get contact with miroku, I think you can ask her to send your mini letter to her japanese penpal who might be able to give it to another member to give to Miichan. (:
TTLuver497's idea is better~...
(Wow it's been a long time since I made a post on jphip...)