Well, thanks for all the replies guys, alot of the ideas you've had could be right, but im really not sure.
For one thing, if it was a person i didn't notice then that could be right, but because it was a 2.5 sec exposure, i would of thought that she would have moved somewhat during the shot, thus blurring it. second thing is, i took a second photo seconds after the first (force of habbit, just incase first doesn't come out) and shes not there.
For her to already be standing there and stay completely still is understandable, but for her to leg it out of the shot in the couple of seconds before i took the second picture, without me noticing, thats where i can't see it being a person.
I understand you guys just have my word on this one that i didn't see her, it was 3am afterall and i was a little drunk by this point so you could be right. But i can tell you honestly that im not trying to hoax anyone. Just trying to get some idea of how that creepy women got in my nice shot of a tree......
Thanks again