Trivia: When Willow is describing her evil twin, she uses the phrase "And I think I'm kinda gay." She says the exact same thing to Dawn during Tabula Rasa when they have all lost their memory.
Trivia: At the end of the episode, after vampire Willow has been returned to her reality, Willow talks about her evil twin. She says that she thinks her double was a little gay or something to that effect. Angel then begins to mention that the vampire personality of a person is a kind of mirror of what the person is or can be, but stops short of finishing the sentence. This is a hint to Willow's coming out of the closet about being a lesbian later on in the series.
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