I read that at Whedonesque. Emmie gets around.
I found it a little jumbled and hard to make sense of. I think I figured it out though. My problem was I didn't take time to think about the terminology. OK, let's see if I've got my Sci fi time terminology straight then.
Time Loop - Not mentioned here, but it's important one sees the difference between a loop and a fold I think. A time loop is a Groundhog Day style loop in time in which a past and future end point loops endlessly, or until the loop is broken, as we saw in the B-6 ep Life Serial.
Time Fold - With a time fold, time folds from a future event to a past one initiating the time line from the future into the past a la Terminator. Time then continues onward from the future end-point. It doesn't stop at the end point, then continuously loop back like it does in a loop.
Time Paradox - The kind of conflict we see in Back to the Future where Marty has to make sure his Mother and Father get connected, or he won't exist. If they don't hook up Marty can't be born. That would be a time paradox.
Time anomaly - Rips in time, or what Willow calls a time rift through which one can pass from one time to another. We see these in Primeval.
OK so Emmie is postulating not a loop in time but a fold. Dark Willow wants Buffy to see Fray's future, so she creates a fold from Fray's future to Buffy's past. She brings Buffy forward in time through a rift, or anomaly to show her how awful it is in the future, or at least that's what Buffy sees.
Huh? Wouldn't that make Buffy want to do anything she could to avoid that future, starting with preventing Willow from going dark? I don't get the logic there.
What would make more sense is if Dark Willow was disappointed with the way things turned out the first time, so she wanted to alter them - thus the suicide. Maybe the way things unfolded this time is not the way Dark Willow remembers them the first time they happened.
What if the first time Past Willow came to get Buffy she did look, see Dark Willow, fight her, and die, thus not a time fold but a time loop caused by a time paradox would be created. This would offer an explanation to the twice quoted "it's not how you die, it's who kills you". When Buffy kills Dark Willow the paradox is resolved, and the loop is broken.