What if Ahsoka managed to strike Vader down? Would she have fallen to the dark side? Then what? I think it would be interesting to ponder about how the aftermath of Ahsoka's revenge would have impacted her, and the greater implications on how galactic history would have been changed.
Well, she could hijack Vader's TIE, I suppose. Or, depending on when in the course of the fight she killed him, fly away from Malachor with Kanan and Ezra or something.
Hmm, that would be interesting if Palpatine took her on as his apprentice or something if she did fall.
*Ahsoka cuts Vader's head off*
"Shit, might as well see who's behind that mask"
*Ahsoka takes the helmet off*
"JESUS ****ING CHRIST"
*Ahsoka is scarred for life and/or kills herself*
Registered: Oct 2009
Location: Miami Metropolitan Area
The Emperor finds a new apprentice, the first three episodes go very differently. How I can't say. It's possible that Luke loses to the Emperor in the end without Vader there to intervene at the crucial moment.
I'm pretty sure she already knew who Vader was, she might have been in denial, but she knew it was him as soon as she reached out with the force and felt his presence. The big "No!" shout was her realizing that it was Anakin.
__________________
“Where the longleaf pines are whispering
to him who loved them so.
Where the faint murmurs now dwindling
echo o’er tide and shore."
-A Grave Epitaph in Santa Rosa County, Florida; I wish I could remember the man's name.
Ahsoka knew subconsciously, but her actual, legitimate realization that Vader = Anakin wasn't until she cut off his mask and he called out to her. Dave Filoni confirmed that was the case I believe in the finale's subsequent interviews.