This has happened to me just last year, actually. I was 'dropped' after being friends with this particular person (who was also my only bridesmaid at my wedding) for 11 years. I received a birthday card last year and have received no correspondence since (a year ago now). I have texted once (in January this year) but never got a response, and still haven't to this day. DH sent her a PM on FB (around Feb/March this year) but she did not respond to this either. I do not want to phone as she's made it plain that she doesn't want to continue the friendship...we used to only meet once or twice a month, then down to once every few months (once DC came along).
She is single and does not plan to have a family of her own. We could leave it months but still be able to chat away like we'd only been talking yesterday, it was that kind of friendship, IYKWIM? However, I do not want to push the issue and after speaking to another friend about the dilemma, my instinct has been right not to pursue and find out why said friend isn't getting in touch any more. It would look quite pushy, and desperate.
I just have to respect her decision that she doesn't want to be friends after all this time. Does having a family mean you cannot carry on a friendship if your friend chooses the opposite path in life to you?? I do feel hurt, but it's one of those situations in life where you cannot force someone to be friends with you, it's their decision and I have to respect that.
So, OP, in a nutshell, I know what you're going through.