Social Dilemma - How Would You Handle This Embarrassing Situation?

Okay, this happened to me yesterday, and I was and am very embarrassed by it, so I want to know what you would have done in this situation.  So of course, everyday, I get my mail and bring it into the house.  A lot of the time, I'm preoccupied with the dog and the cat so I'm not really paying attention when I'm opening the mail.   Anyway, long story short, as I'm opening each letter and looking at it, I open one and it took me a minute to realize it wasn't mine.  It was a neighbor's who lives one street over, and it was her bank statement.  Now we don't really know each other very well.  She lives at 37 Rock and I live at 37 Cap, so sometimes our mail gets mixed up and that's really the only way we know each other.  Anyway, I felt really really bad.  I was going to try to tape it back up, but I had really ripped it open.  I was going to throw it away, but that wouldn't have been right, so I called a friend and asked for advice, and she said just tape it up, put a note on the envelope that you accidentally opened it and leave it in her mailbox.  That's what I did, but I didn't sign my name.  I just wrote the note anonymously.  And I have SUCH guilt over it.  Do you think I should call her and tell her it was me, should I just leave it alone?  HELP!! I'm desperate for your advice.  What would you do?