I don't know of any way for you to 'know' for sure. I would suggest this, if she has been honest with you while you have known her and if she is right about what she has 'seen' than I would trust her being truthful.
It is up to you to decide if you do or can believe and trust her.
How do you 'explain' then her 'knowing' what she knew ? Other than an 'obvious' scrape on your knee that wouldn't be hard to discern. Only the other examples would tell them if she is the 'real' deal.....
Contrary to popular belief, psychic doesn't mean you can see the future. Sure, psychics CAN, but precognition is nowhere near the full spectrum of psionic ability. With the psychic method of precognition, you can meditate on and dream about a specific point in time, or clairvoyantly find it. Try testing her with Zener cards to evaluate her clairvoyance. If she gets it all wrong, try setting up something for the next day, and ask her to meditate and dream about it.
she could be a couple things, some simple test could help figure out what. if you two are really close, you could have a bond, sense when the other's hurt, you know?
Sorry for reading "past" wrong. However, you obviously don't know what an actual psychic is. The two actually psychic methods of looking into other times are the ones I stated. Moonlite should test them, and see if it was just a coincidence.
Nekoshema makes a good point, but that would still technically make your friend a psychic. The title refers to a person's awareness of the "beyond". I see no reason not to believe your friend, but I'd be cautious until you are absolutely certain (that means no playing the lottery). Everyone has the capability in them, to some it just comes more naturally than others.
I've decided to believe what she says, just because our bond is very strong, and she's believed me in many matters that had the possiblity of doubt. I plan on having a serious talk with her about it, but until than, the only thing I can do is believe.
As for some comments, I didn't have any signs of being hurt. I was wearing track pants, actually :P I just had one question about your suggestion, fgopl, what are zener cards and how would they help? I'm planning on googling it right now.
Nekoshema, I have seriously considered that possibilty. We're not related in any way whatsoever, we've been raised in two completely different ways, and I only met her three years ago, but something in your suggestion holds valid possibility and truth. Again, I'm going to research it.
My friend has always been more in tune to her 'physcic' side, maybe it is just natural for her.