This sounds like the sort of plan you see on daytime television, and remember how those always go wrong? The least bad thing that could happen is nothing... she takes one look at the note, goes "Eeeew" and throws the lot in the trash. The options get worse from there.

I was 13 the last time I tried to control people with anonymous notes, and 16 the last time I tried to contact a girl I fancied that way. I learnt better. Man up and ask her out, or forget it.