
End Of Days - S7-E21
Revealing mistake: When Buffy finds Faith and the Potentials in the sewers she throws an Ubervamp across the room. When we see the Ubervamp from behind you can also see the actor's blue boxer shorts sticking out of the Ubervamp costume.
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