I had a nightmare... Help?

Okay so two of my best friends recently got into a relationship. I helped him get her, even though she saw him as just a friend. It was complicated but in the end she wound up liking him too and asked him out, they are now together (:

I have to admit after this I was terrified of becoming the third wheel. But they both keep me involved and see me together and seperately, and everything is just as it was before, except they're together now.

But last night I had a nightmare involving them and it really bugs me. Help?

We were walking outside a shopping centre we all live near, not sure why. They were holding hands and I was trailing behind, though still involved in the conversation. Then this man came behind me and grabbed me and he had a knife, and he was pulling me backwards. I was screaming to them for help. I remember saying "Help me," and "Please don't leave me," and "I need you," and I was crying and kicking out and everything. But they didn't turn around, I don't think they noticed. They didn't even achknowledge me at all and carried on walking like normal. And then I woke up.

I don't know what this means and I talked to the boy in the relationship about it, but he didn't try to come up with a solution. I winded up telling him that I didn't have a problem, I just wanted to tell someone. Truth is, I really want to know what this means and why.

If it's relevant at all, I'm fourteen and they're both fifteen, I'm a school year below them. I'm a girl. I've been best friends with the girl since I was seven and best friends with the guy since I was nine.

Thanks (: