Lover's Walk - S3-E8
Continuity mistake: In the episode Lover's Walk, when Spike is threatening Willow at the factory, in the long shots Willow's hair is up over her face, and in the close-ups it isn't. The pointed bit of the bottle is at the top or bottom in different shots too. (00:19:20)
Answer: She has superpowers, ergo fast movement. The reason she outruns him so easily in "Touched" is that she stops trying to actually fight him and just dodges instead.
Shay