You can still have her as your BFF...my BFF does not have kids, we have been friends since Jr. High. Over 20 years of friendship. It was not always easy, especially when I had kids.
You have to make it work. Sometimes I listen, sometimes she listens...and sometimes neither of us listens to the other one.
When I was pregnant with my first and I would call her and complain about morning sickness she once said "I think that is all in your head, women who have morning sickness only think they have it, it's not real"...WTH? I had to remember she has never experienced this. She's ignorant of what really happens.
She would see old friends and people would ask about me and she says "oh she's a breeder now"...but because I know her (better than her sisters do) I know she was slightly jealous and slightly pissed as someone else was going to get my attention.
In the last few years we've talked and it's come to light she can't have kids we are in our mid 30s and she won't ever get to have kids (unless she adopts but right now that is not something she wants to do)...
People without kids don't get it as someone said below.
Don't give up...Sometimes we don't talk about the single life or the married/kids life...we just talk about books, movies...things that take our minds off of our everyday lives. Try talking about something other than kids/single life.