Then again, it could simply be artistic license
used by the art department and director because it worked better than having the wolves disappear and everyone KNOW it's a vision. It would have been a dead giveaway. One of the only places on earth where they will be called on it is here on the Lex, and they knew that.
It worked in the movie. For most everyone, their presence simply didn't make a difference. Only here to the faithful few, and perhaps in SM's notes, did the wolves make any difference at all.
It isn't exactly the first time one of the movies altered canon a bit. Can I hear an
Here is the reason they had to ignore canon: Alice doesn't see what she has never been. The wolves intervention completely eradicated her vision of the Newborn army in Eclipse. There is NO
way that she could have seen the battle at all
once the wolves were involved.
Now, here is one possible way out I thought of (it is weak since SM made it pretty clear the wolves made all futures invisible to Alice): She was showing Aro HIS future, not just that of the Cullens. Aro had made up his mind to attack. If he hadn't, the future would not have been clear. Perhaps, since his future involved the wolves, and she was showing him his future and his end, this made it possible for her to see them. They weren't a key to that vision, just a part of it. She saw their lives as a side product of showing Aro his.
Thoughts? This topic is right up my ally and I'd love to hear what you all think!