What does it mean to dream about a dead friend?

[Monday43]

I was dreaming about something last night, I don't even remember what it was and suddenly my friend was there. She died in a horseback riding accident in October, she was 23. Before she died we had been talking on facebook but I never answered her last message. Anyway, we both rode horses and wanted to go for a ride together but never got to because I moved to Alaska. But in the dream she was riding with me and we were racing our horses, she beat me by a short distance. After the race we were both in a room with people I didn't recognize and after a while I said something about her death and she smiled and gave me a hug and headed for the door and I called after her that we would hang out soon and she said "Yes" and then I woke up with tears in my eyes. Does it mean anything when you have a dream like that, I feel like it was really her.