The ethics of friending

I still don't totally understand what I'm supposed to be doing with Facebook.  I am however, experiencing the issues associated with friending.  There's a girl I know who pinged me on LinkedIn a little while back and even included a personal message about how I wasn't in California like I was supposed to be (don't bring it up; it makes me cry).  Haven't seen her since right before the clerkship.  I was in her wedding my 2L year of law school.  So I e-mailed her back to see if she wanted to get together now that I'm back in town.   No response.  That's cool.  Maybe she's busy.  She's on Facebook so I sent her a friend request.  Nothing.  Silence.  Is she mad I didn't invite her to my wedding?  It was a small affair!!  If she would e-mail be back, maybe she would know that.  It's like the unrequited friend request is the confirmation of the death of a friendship.   So sad.  I mean, I know I totally suck at keeping in touch, but is that really a reason to not accept a friend request from a bridesmaid??