I had that happen to me. I was depressed for a whole 3 months because I felt like I had no real friends at my new school.. But all I could do is keep in touch with my old friends through Facebook and chatting. And I made new close friends after a few months later too. Just keep in touch, remember things will get better (because it did for me too), and everything will work out fine
I moved across the country in June. Away from all my best friends and everything. We are still just as close and we talk almost everyday. You'll figure out if your friends are true if you still are just as good as friends as you were. You don't have to talk every single day, though. :) and twitter is really good for keeping up with your friends.
You realize that what your mom is doing is not JUST about you. She likely has a reason, new job, lower housing costs, etc. & that in the long run it will all work out. Remember this move won't be your last and you'll make new friends. Trust me.